Mirror-Induced Behavior in the Magpie (Pica pica): Evidence of Self-Recognition

Helmut Prior
Institut fü r Psychologie
Goethe-Universität
Frankfurt am Main, Germany

Ariane Schwarz
Institut fü r Kognitive Neurowissenschaften
Ruhr-Universität Bochum
Biopsychologie, BochumGermany

Onur Gü Ntü Rkü N
Institut fü r Kognitive Neurowissenschaften
Ruhr-Universität Bochum
Biopsychologie, BochumGermany

Mirror-Induced Behavior in the Magpie (Pica pica): Evidence of Self-Recognition

Comparative studies suggest that at least some bird species have evolved mental skills similar to those found in humans and apes. This is indicated by feats such as tool use, episodic-like memory, and the ability to use one's own experience in predicting the behavior of conspecifics. It is, however, not yet clear whether these skills are accompanied by an understanding of the self. In apes, self-directed behavior in response to a mirror has been taken as evidence of self-recognition. We investigated mirror-induced behavior in the magpie, a songbird species from the crow family. As in apes, some individuals behaved in front of the mirror as if they were testing behavioral contingencies. When provided with a mark, magpies showed spontaneous mark-directed behavior. Our findings provide the first evidence of mirror self-recognition in a non-mammalian species. They suggest that essential components of human selfrecognition have evolved independently in different vertebrate classes with a separate evolutionary history. Citation: Prior H, Schwarz A, Gü ntü rkü n O (2008) Mirror-induced behavior in the magpie (Pica pica): Evidence of self-recognition. PLoS Biol 6(8): e202.

Introduction

Since the pioneering work by Gallup [1], a number of studies have investigated the occurrence of mirror-induced self-directed behavior in animals of a great range of species. Most animals exposed to a mirror respond with social behavior, e.g., aggressive displays, and continue to do so during repeated testing. In a few ape species, however, behavior changes over repeated presentations with a mirror. Social behavior decreases, and the mirror is used for exploration of the own body. This suggestive evidence of self-recognition is further corroborated by the mirror and mark test. If an individual is experimentally provided with a mark that cannot be directly seen but is, however, visible in the mirror, increased exploration of the own body and selfdirected actions towards the mark suggest that the mirror image is being perceived as self. Fairly clear evidence of this has been obtained for chimpanzees [1], orang-utans [2], and pygmy chimpanzees [3]. In gorillas and gibbons, some authors reported failure of self-recognition [4,5] whereas others reported positive findings in at least one individual [6,7]. It should be mentioned that even in the chimpanzee, the species most studied and with the most convincing findings, clear-cut evidence of self-recognition is not obtained in all individuals tested. Prevalence is about 75% in young adults and considerably less in young and aging individuals [8]. Findings suggestive of self-recognition in mammals other than apes have been reported for dolphins [9] and elephants [10]. In monkeys, nonprimate mammals, and in a number of bird species, exploration of the mirror and social displays were observed, but no hints at mirror-induced self-directed behavior have been obtained [5]. Does this mean a cognitive Rubicon with apes and a few other species with complex social behavior on one side and the rest of the animal kingdom on the other side? This might imply that animal selfrecognition is restricted to mammals with large brains and highly evolved social cognition but absent from animals without a neocortex. Within humans and apes, self-recognition might reflect a homologous trait, whereas findings in other mammals hint at a convergent evolution. A likely reason for such convergent evolution of self-recognition in dolphins and elephants is the convergent evolution of complex social understanding and empathetic behavior [10]. If self-recognition is linked to highly developed social understanding, some birds species, in particular from the corvid family, are likely candidates for self-recognition, too. A number of studies from the past years have demonstrated an elaborated understanding of social relations, in particular during competition for food. It has been shown that own experience in pilfering caches facilitates predicting similar behavior in others [11], and that magpies [12] and scrub jays [13] remember who of their conspecifics observed them during storing. Thus, foodstoring birds might be particularly apt in empathy and perspective taking, which have been suggested to coevolve with mirror self-recognition [14].

An investigation of self-recognition in corvids is not only of interest regarding the convergent evolution of social intelligence, it is also valuable for an understanding of the general principles that govern cognitive evolution and their underlying neural mechanisms. Mammals and birds inherited the same brain components from their last common ancestor nearly 300 million years ago and have since then independently developed a relatively large forebrain pallium. However, both classes differ substantially with regard to the internal organization of their pallium, with birds lacking a laminated cortex but having developed an organization of clustered forebrain entities instead [15]. In some groups of birds and mammals, such as corvids and apes, respectively, brain tobody ratios are especially high [16], and these animals are able to generate the same complex cognitive skills [17]. This is indicated by feats such as tool use and tool manufacture [18,19], episodic-like memory [20], and the ability to use own experience in predicting the behavior of conspecifics [11]. Although it has been shown that some birds, e.g., Grey Parrots [21], use mirrors with skill in order to localize and discriminate objects, no experimental evidence of selfrecognition has been obtained in birds so far.

In the present study, magpies were chosen for several reasons. They are food-storing corvids that compete with conspecifics for individually cached and memorized hoards. They thus live under ecological conditions that favor the evolution of social intelligence [12,17]. They achieve the highest level of Piagetian object permanence [22], which is also achieved by apes, but not by monkeys. In addition to showing social understanding during competition for food [12], magpies are curious and prone to approach new situations, making them ideally suited for an experiment that requires spontaneous interaction with a new and puzzling context.

Mirror behavior in animals goes through several stages. In all species tested so far, inspection of the mirror and social behavior has been observed. In species with mirror selfrecognition, some of the individuals also show evidence of inspection of their own body and testing for behavioral contingencies after familiarization with the mirror. For example, they move back and forth in front of the mirror, and this might indicate that they check to which degree the mirror image is coupled to their own movement. Individuals achieving this stage often also pass the mirror and mark test.

In our experiments, we began with open mirror exploration, and then we assessed preference for the mirror and quantified mirror-induced behaviors under highly standardized conditions in a two-compartment cage with one side containing a mirror. Subsequently, we investigated spontaneous self-directed behavior in individuals provided with a mark, and finally, we carried out a series of mark tests and control tests that were designed as to ensure appropriate control and exclude the possibility that findings are due to operant conditioning. Marked individuals (cf. Figure 1) were given a small number of tests, and we applied two types of appropriate controls. The birds were either marked with a brightly colored (yellow or red) or a black (sham) mark. Handling and somesthetic input was thus identical for all marks, but the black mark was practically not visible on the black feathers of the throat. In half of the trials, a mirror was placed with the reflective surface towards the animal; in the other half of trials, the mirror was replaced by a nonreflective plate of the same size and position. Therefore, the possibility to see a colored spot on the own body by means of the mirror was the only predictor of an increase of behavioral activities towards the marked (or sham-marked) region ( Figure 2) in the different experimental conditions. Each bird was tested twice in each of the conditions, resulting in eight tests per bird.

Results and Discussion Open Mirror Test

In baseline trials with a nonreflective plate, there was no remarkable behavior in front of the plate in any of the individuals. With a mirror, the behavior of the magpies clearly differed. Initial exploration of the mirror was characterized by approaches towards the mirror and looks behind the mirror. Also, social behavior occurred, such as aggressive displays towards the mirror and jumping towards the mirror as in a fight. In three individuals, Gerti, Goldie, and Schatzi, social behaviors were transient, i.e., they were

Author Summary

A crucial step in the emergence of self-recognition is the understanding that one's own mirror reflection does not represent another individual but oneself. In nonhuman species and in children, the ''mark test'' has been used as an indicator of self-recognition. In these experiments, subjects are placed in front of a mirror and provided with a mark that cannot be seen directly but is visible in the mirror. Mirror self-recognition has been shown in apes and, recently, in dolphins and elephants. Although experimental evidence in nonmammalian species has been lacking, some birds from the corvid family show skill in tasks that require perspective taking, a likely prerequisite for the occurrence of mirror selfrecognition. Using the mark test, we obtained evidence for mirror self-recognition in the European Magpie, Pica pica. This finding shows that elaborate cognitive skills arose independently in corvids and primates, taxonomic groups with an evolutionary history that diverged about 300 million years ago. It further proves that the neocortex is not a prerequisite for self-recognition.

reduced already on the second exposure or completely ceased to occur. In the other two birds, Harvey and Lilly, social behaviors, in particular aggressive and submissive displays, continued to be frequent. On several trials, Harvey also picked up little, but conspicuous, objects and posed, accompanied by wing-flipping, in front of the mirror holding the objects in the beak. This courtship-like behavior vanished after a few trials, and was never seen on later tests, which were characterized by aggressive displays. In the open mirror experiment, however, mainly two of the birds (Goldie and Harvey) took part, whereas the other three birds only occasionally visited the location of the mirror. Therefore, we proceeded with a highly standardized protocol for mirror exploration.

Mirror Preference and Standardized Mirror Exploration

In these tests, birds could choose between two identical compartments of a cage, one equipped with a mirror and the other with a nonreflective plate instead of the mirror. Table 1 gives the time the birds spent with view on the mirror and shows how many bouts of close inspection of the mirror, of looks behind the mirror, of contingent behavior, and of social behavior were displayed by the birds. Three of the individuals (Gerti, Goldie, and Schatzi) spent a considerable amount of time in the compartment with the mirror, whereas the two other birds (Lilly and Harvey) appeared to avoid the compartment with the mirror. In the three birds with a preference for the mirror, behavior was characterized by close visual exploration of the mirror image (see Video S1 for an example). In addition, Gerti and Schatzi repeatedly looked behind the mirror and showed several bouts of behavior indicating contingency testing. Subjects moved their head or the whole body back and forth in front of the mirror in a systematic way (see Videos S2 and S3 for examples). In Goldie, contingent behavior was not demonstrated in this test, but demonstrated later in the mark test (see Video S4). Harvey and Lilly never showed any hint of such behavior. It is noteworthy that those birds that had a high interest in the mirror and also showed social displays only in the first tests were those that showed at least some evidence of self-directed behavior on later tests.

Mark Test

In a first exposure to a mirror with a mark, three out of five birds showed at least one instance of spontaneous selfdirected behavior (see Video S6 for an example in the subject Schatzi). In the subsequent quantitative analysis, which compared the behavior in the mirror and mark condition with a condition without a mirror, mark-directed behavior (cf. Videos S5 and S7) in two of the birds, Gerti and Goldie, was significantly higher in the critical mirror and mark condition than in the other conditions. There were no instances in any of the birds of pecking at the reflection of the mark in the mirror. Figure 3 shows the quantitative amount of behavior towards the mark region as a proportion of all behaviors towards the own body for these two birds. Contrary to the absolute counts, this proportion will only increase with a specific effect on mark-directed behavior but not as a consequence of a possible overall increase in behaviors towards the own body. It can be seen that mark-directed behavior was only significantly enhanced when a mirror was present and the mark was colored and thus visible for the birds. The detailed frequencies in the different conditions are given in Table 2. The comparison of the frequencies of behaviors directed towards other parts of the body clearly shows that the mark-directed behaviors in the mirror and colored mark condition cannot be explained by a general increase of behavioral activity. A specific increase of markdirected behavior in presence of a mirror is corroborated by the fact that mark-directed behavior ceased within trials as soon as the bird had removed the mark (see Video S8). In Figure 4A, performance of Gerti in a single test with change of marks is shown (see also Table 3). As this is only one test, findings should be interpreted with some caution, but consistent with the between-sessions comparison in the first test series, mark-directed behavior was high when the mark was visible in the mirror and low with the black control mark that was not visible. Figure 4B shows the results of an additional test with two sessions in the mirror and colored mark (yellow) condition and two control sessions with colored marks and a nonreflective plate instead of the mirror. Also in this case, mark-directed behavior only occurred with the mirror. With colored mark and mirror, over the two trials, there were five mark-directed actions per trial and 12 actions towards the rest of the body, whereas there was no markdirected behavior at all when the bird wore a colored mark but no mirror was present. Again, findings clearly show that this significant difference cannot be explained by an unspecific increase in overall behavioral activity, as the overall rate of behaviors directed towards the own body was similar. These quantitative data are rather conservative as Gerti and Goldie removed the mark after a few minutes on most of the trials with a color mark and a mirror, and after removal of the mark, no mark-directed behaviors occurred (see Videos S5, S7, and S8 for different aspects of markdirected behavior in the subject Gerti).

Whereas mark-directed behaviors were virtually absent when the birds were tested without a mirror but with a colored mark, there were a few instances of mark-directed behavior in the mirror condition with a black control mark ( Figure 3). It may well be that the black paper mark was slightly visible on the black plumage. This is supported by the observation that if the black mark condition elicited behavior, it was in the ''mirror present'' trials. This is an indirect support for the interpretation that the behavior towards the mark region was elicited by seeing the own body in the mirror in conjunction with an unusual spot on the own body.

Evidence from the quantitative data is corroborated by the qualitative behavior of the birds. Self-directed activity began after looks into the mirror and visual exploration of the mirror image, and it ceased as soon as the bird had successfully removed the mark (see Video S5). This is unlike chimpanzees, which, after discovering that the mark is inconsequential, rapidly lose interest [23]. The reason for the difference could be that bird's feathers are of considerably higher importance for survival than a patch of hair in chimps. This interpretation is supported by data showing that birds spend about one quarter of their resting time with  Yes The three birds with evidence of mirror-induced self-directed behavior on later testing spent a higher amount of time in the compartment with the mirror. Interest in the mirror tended to decline over repeated trials. All other scores are based on an event-sampling procedure. During ''close inspection,'' the bird is very close to the mirror and inspects the image, accompanied by turning and tilting of its head. ''Contingent behavior'' was counted when a bird moved repeatedly leftwards and rightwards or back and forth in front of the mirror. All social behaviors displayed in these tests belonged to the agonistic context (see Materials and Methods for details and Video S9 for an example). For comparison, the three columns on the right show whether the subjects showed social behavior on later testing and whether they showed self-directed behavior in front of the mirror in the mark test or on other occasions. A negative sign (À) indicates no occurrence of the behavior, and a plus sign (þ) indicates that the behavior was shown. Parentheses around the plus sign for the subject Schatzi indicate that mark-directed behavior was enhanced but did not reach statistical significance. doi:10.1371/journal.pbio.0060202.t001
À À 2 Inactive - - - - 3 Inactive - - - - 4 Inactive - - - - 5 Inactive - - - -
preening and are often seen to interrupt sleeping in complete darkness only to preen [24]. Two of the other three birds reacted to the mirror with excited behavior characterized by frequent jumping and running within the cage, and the last bird showed a high number of attacks towards the mirror in one trial (see Video S9), but not in the other. The subject Schatzi, which had shown spontaneous mark-directed behavior during an earlier exposure, showed no significant mark-directed behavior in this series of tests, although there were two instances of markdirected behavior in the mirror and color condition and no mark-directed behavior in the other conditions.

Interestingly, the behavior in the mark tests corresponded to interest in the mirror in the standardized mirror exploration test. Those individuals that showed at least one instance of mark-directed behavior were the same that had shown a high interest in the mirror in the preference test, and the individual strongly avoiding the mirror in the choice test (Harvey) showed a high amount of attack-like behavior in the mark test.

One might ask why rather clear evidence was observed in two individuals and weaker evidence in another one, but not in all of the five birds. The proportion of positive findings is, however, well in the range of what has been found in apes. In chimpanzees, the species best studied and showing the clearest evidence of mirror-induced self-directed behavior, a considerable number of individuals typically produce negative findings [8,25]. Of 92 individuals tested by Povinelli et al. [8], only 21 demonstrated clear and nine weak evidence of self-exploration, with about 75% prevalence in young adults of 8 to 15 y. Only half among those with clear evidence of self-exploration passed the mark test. Thus, our data do not only qualitatively, but also quantitatively, match the findings in chimpanzees. As a note of caution, we would like, however, to emphasize that the number of birds we tested is too small for a definitive estimate of the distribution within the population. Thus, further studies must assess whether the   typical frequency of mirror-induced self-directed behavior in magpies is comparable to that in chimpanzees. Altogether, results show that magpies are capable of understanding that a mirror image belongs to their own body. We do not claim that the findings demonstrate a level of self-consciousness or self-reflection typical of humans. The findings do however show that magpies respond in the mirror and mark test in a manner so far only clearly found in apes, and, at least suggestively, in dolphins and elephants. This is a remarkable capability that is at least a prerequisite of selfrecognition and might play a role in perspective taking. It thus could be essential for the ability of using own experience to predict the behavior of conspecifics [11]. Magpies are corvids, which belong to the order of Passeriformes, a phylogenetic group characterized by large brains relative to body weight [26]. The relative brain size of passeriform birds is similar to primates in allometric analyses, and within the Passeriformes, corvids stand out with particular high relative brain size [27]. Thus, magpies belong to a group of animals with very high relative brain size (see also Table 4).

We used a small number of tests as it was crucial to ensure that possible self-directed behavior of the birds represented a spontaneous response to seeing the own body in the mirror. Epstein et al. [28] reported that prolonged operant conditioning of isolated components of the mark test in pigeons could produce a behavioral pattern that superficially looks like mirror-induced mark-directed behavior. This study could, however, not be replicated [29], and these authors also found reduction of self-directed behavior in pigeons in the conditions with a mirror, which strikingly contrasts with  Since the percent brain-weight measure favors small species, an alternative depiction would be the encephalization quotient (EQ). The EQ indicates the extent to which the brain weight of a given species deviates from the expected brain weight based on a standard species of the same taxon or a common allometric regression. However, equations for allometric lines vary among studies, and different data are often used in different studies. To our knowledge, EQs for the species in Table 4 were never calculated with the same allometric regression. doi:10.1371/journal.pbio.0060202.t004 our findings in magpies. Additionally, extremely long periods of exposure to mirrors without specific training of selfrelated actions did not produce any kinds of behavior that was centered on the mark in monkeys [30,31]. Lastly, the mark test is only one piece of evidence of mirror-induced selfrecognition in animals. Of equal importance are previous inspections of the mirror, such as during looks at the back side of the mirror, and exploration of mirror properties, such as during contingent behavior [1,8,10,32]. Our magpies showed self-related behavior in front of the mirror after a rather short cumulative exposure time and without being specifically trained to do so. In addition, when confronted with mirrors the first time, they displayed similar sequences of behavior as described in apes [1,2,3,8,32]. Although the mark test has been criticized [33,34], the main objections have been ruled out [23], and it remains one of the most useful tests for self-recognition in comparative studies [35]. When magpies are judged by the same criteria as primates, they show self-recognition and are on our side of the ''cognitive Rubicon.'' One should keep in mind that though mirror selfrecognition reflects a crucial step in the emergence of selfrecognition, the fully fledged capacity is complex, and comparative [36,37], clinical [38], and developmental studies [39] suggest an overall gradual development of this capacity.

Cognitive and neurobiological studies of the last decade have shown that birds and mammals faced a similar selection pressure for complex cognitive abilities, resulting in the evolution of a comparable neural architecture of their forebrain association areas [40] as well as their cognitive operations [17,[41][42][43]. This high degree of evolutionary convergence is especially visible for the cognitive abilities of corvids and apes [17]. By demonstrating self-recognition in the mirror by magpies, the present study shows that even the neural capacity for distinguishing self and others has evolved independently in the two vertebrate classes and that a laminated cortex is not a prerequisite for self-recognition.

Materials and Methods

Five adult hand-raised magpies served as subjects throughout the study. These birds had been used before in a study on the development of object permanence and in patterned string problems. Investigation of behavior towards a mirror consisted of three steps.

Open mirror exploration. In a 4 3 4-m room, a mirror 55-cm wide and 40-cm high was placed on the ground, leaning against a pole, and slightly tilted. The position of the mirror was in the middle of one of the walls with about 1.5-m distance from the wall, allowing the birds to move around the mirror. The tested subject could move freely in the room. After a baseline trial with the mirror replaced by a grey, nonreflective plate, five test sessions of 30-min duration were given to each of the birds. The behavior of the birds was observed from an adjacent room by means of a video system, and trials were videotaped.

Mirror preference and standardized mirror exploration. For a quantitative estimation of the interest in the mirror, a cage with two opposite compartments was used. Compartments 60 3 100 3 60 cm (length 3 height 3 width) were identical except that there was a mirror at the end of one of the compartments and a grey, nonreflective plate of the same size in the other compartment. Between the compartments, there was a partition with two overlapping walls so that the birds could move freely between compartments but could not see from one compartment into the other. Each of the birds received five consecutive trials of 20 min on separate days. The time the birds spent in the compartment with the mirror was measured, and based of the videotapes bouts of close mirror inspection, looks behind the mirror, bouts of contingent behavior, and social behaviors were counted.

Mark test. In the mark test, each subject was involved in eight test sessions with the conditions, (1) mirror and colored mark, (2) mirror and black mark, (3) no mirror with colored mark, and (4) no mirror with black mark. One session lasted 20 min. Each condition was replicated once, and two colors, either yellow or red, were used for the colored mark. Thus, our subjects were marked in all conditions to prevent cueing by somesthetic input, but the black mark in condition 2 was practically not visible on the black feathers of the throat. Such sham marking, which also had been used in studies with dolphins and elephants [9,10], has the advantage that no anesthesia is needed, and it provides a rather rigorous control as except for the difference in appearance, every detail of the procedure is perfectly matched to the conditions with a color mark. In the no-mirror controls, the mirror was replaced by a nonreflective flat grey plate of the same size and in the same position. Conditions, including usage of the two marking colors yellow and red, alternated in balanced order. Colored marks and black control marks were fixed below the beak onto the throat region ( Figure 1). Different pigeon breeds are blind to this area even during strong convergent eye movements [44]. In magpies, the visual field has not been studied in detail. However, the position of the eyes and the optical axis is comparable to that of pigeons. Thus, the assumption is justified that the spot used for marking was far outside the magpies' visual field. This is, furthermore, strongly corroborated by the behavioral data, as there was virtually no mark-directed behavior if magpies wore a colored mark in the no-mirror condition. In each of the conditions, every detail regarding the handling of the birds was identical, except that the birds could see the reflection of the yellow or red mark in the mirror and colored mark condition, but not in the various other conditions.

Scoring of behaviors. Before testing, we protocolled all behaviors observable. Then two observers (others than those assessing the mirror test) independently scored videotapes several times, and a list emerged of 18 behaviors with high interobserver agreement and high reliability over repeated scorings. The list included behaviors not relevant for the question of this study (like moving slowly or fast or jumping in the cage), and for the present study, we focused on a subset of behaviors diagnostic of the animals responding to the mirror. First, social behaviors that could be observed with high reliability were agonistic displays, either submissive or attack-like. During submissive behavior, the bird faces the mirror (or another bird), has its back lowered, its wings slightly spread, and often flips its wings. During aggressive displays, the bird takes an upright position with elongated neck and/or performs attack-like behaviors towards the mirror (c.f. [45] for pictures of typical displays by magpies). Secondly, we recorded all behaviors directed towards a bird's own body, such as touching any part of the body with the beak or the foot, and we assessed whether the action was directed towards the regions near the mark or elsewhere.

Before the first mark test, birds were familiarized with the experimental cage and the mirror for at least 5 d. The experimental cage was 120 3 100 3 60 cm (l 3 h 3 w) and had a grid floor. The walls also consisted of a grid except for one long wall, which in most of the tests consisted of Plexiglas in order to provide a good view of the bird. The mirror or the nonreflective plate was always placed on the ground at the same short wall of the cage.

At the beginning of a test, a bird was taken from its home cage and brought to an adjacent room, where the colored mark or the control mark was fixed. The bird was held by one of the experimenters such that the throat region below the beak was exposed. The head of the bird was shielded by the hand of the experimenter holding the bird so that the bird could not see the fixing procedure. The other experimenter then fixed the self-adhesive colored or black mark. Except for the color of the mark, the handling procedure was exactly the same in each of the experimental conditions. Although the dots used for marking were self-adhesive, we prepared them with doublesided adhesive tape in order to ensure good fixation. The weight of a dot was 16 lg and the diameter 8 mm.

After completion of testing of all birds in each of the conditions twice, further tests were applied for the subject Gerti, who showed very clear and consistent self-directed behavior. First of all, a mirror test with four consecutive phases of 5 min was carried out, and in each phase, a new mark was fixed (yellow, blue, black, or red). Secondly, additional tests comparing the behavior in the colored mark and mirror condition with that in the colored mark and nomirror condition were carried out with a normal cage grid instead of a Plexiglas wall in front of the cage. In experiments with dolphins [9], the interpretation of the subjects' behaviors was complicated by the fact that the animals had apparently used the reflecting sidewalls of their pool in addition to the mirror provided by the experimenters. Although reflectance by the Plexiglas front was not likely, we sought additional controls to ensure that the presence or absence of the mirror was the only predictor of differences in mark-directed behavior.

While the birds were being set into or removed from the experimental cage, room lights were switched off. A test began by turning the lights on. Experiments were monitored via a video system from an adjacent room, and all tests were videotaped. From videotapes, the frequency of behaviors directed towards the own body were scored. Actions towards the marked region with the beak or the foot entered the analysis as mark-directed behavior (see Figure  2); all other behaviors towards the own body, such as touching the breast region with the beak, preening of the tail or wings, were considered not mark related. Likewise, all social behaviors, such as aggressive displays in front of the mirror, were scored. Figure 2 shows examples of the behaviors used for quantitative analysis. See also the supplementary material, Video S5-S8. Quantitative assessment of behavior based on the video tapes was carried out independently by two observers (H. P. and O. G.). Their scores were highly correlated (r ¼ 0.98), and the combined score from both assessments was used for further analysis.

Supporting Information

Nine video clips that show relevant behavioral sequences for the subjects Gerti, Goldie, Harvey, and Schatzi.

Video S1. Visual Exploration of the Mirror Image, Four Examples, Subject Gerti The bird is close to the mirror, behaves in a rather quiet way, and explores its mirror image. This behavior contrasts sharply with the agitated and sometimes aggressive behavior as observed in the subjects Harvey and Lilly (see Video S9 for examples). Found at doi:10.1371/journal.pbio.0060202.sv001 (3.89 MB WMV).

Video S2. Behavior in the Preference Test, Schatzi

The bird had a strong preference for the compartment with the mirror and explored the situation intensively. Note the repeated sequences of looks into the mirror and behind the mirror. Found at doi:10.1371/journal.pbio.0060202.sv002 (3.98 MB WMV).

Video S3. Testing for Contingencies, Gerti Gerti is testing for contingencies between her own behavior and the mirror image by moving back and forth and left and right in front of the mirror. Note the behavior after 20 s when Gerti very slowly bends to the left and inspects her mirror image with the mark. We never observed similar behavior in any social interaction between two magpies. Found at doi:10.1371/journal.pbio.0060202.sv003 (1.93 MB WMV).

Video S4. Testing for Contingencies, Goldie Goldie explores his mirror image while moving back and forth and turning his head in front of the mirror.

Video S5. Attempts to Reach the Mark with the Beak, Gerti Gerti tries to reach the mark with the beak, which is not possible. In the second of the two scenes, she finally takes her right foot and successfully removes the mark. Found at doi:10.1371/journal.pbio.0060202.sv005 (3.10 MB WMV).

Video S6. Mark-Directed Behavior with the Foot, Schatzi Schatzi attempts to reach the mark with the right foot. Found at doi:10.1371/journal.pbio.0060202.sv006 (674 KB WMV).

Video S7. Mark-Directed Behavior with the Foot, Gerti Three examples of mark-directed behavior with the foot by Gerti.

The three examples show how the birds used their feet for markdirected behavior. They also show that this behavior, as with markdirected behavior with the beak, is clearly distinguishable from actions towards other parts of the body. Found at doi:10.1371/journal.pbio.0060202.sv007 (2.52 MB WMV).

Video S8. Attempts to Remove the Mark, Gerti The example shows how Gerti tried to support mark removal with the beak by means of bill swipes. Note that after having removed the mark, Gerti turns to the mirror and inspects her mirror image before beginning comfort behavior. Found at doi:10.1371/journal.pbio.0060202.sv008 (2.19 MB WMV).

Video S9. Aggressive Behavior, Harvey Four instances of social, in particular, aggressive behavior in the subject Harvey. In the first two scenes, the behavior shows a transition between submissive and aggressive behavior; the last two scenes represent outright attack-like behavior. In some of the scenes filmed at an early stage of the experiments, Gerti was in a phase of molting. Later scenes show the same subject with full plumage after molting had ceased. Note that birds with lateral eyes fixate objects by viewing laterally with either the right or left eye.

Figure 1 .
1Magpie with Yellow Mark doi:10.1371/journal.pbio.

Figure 2 .
2Examples of the Behaviors That Were Used for Quantitative Analysis (A) Attempt to reach the mark with the beak; (B) touching the mark area with the foot; (C) touching the breast region outside the marked area; (D) touching other parts of the body. Behaviors (A) and (B) entered the analysis as mark-directed behavior; behaviors (C) and (D) and similar actions towards other parts of the body were considered self-directed, but not related to the mark. doi:10.1371/journal.pbio.0060202.g002

Figure 3 .
3Proportion of Self-Directed Behavior towards the Mark Area Expressed as a Proportion of Overall Self-Directed Behavior in Subjects Gerti and Goldie Orange bars refer to tests with a colored mark (yellow or red), black bars to tests with a black control mark (sham condition). In Gerti (p , 0.005, Fisher exact test), as well as in Goldie (p , 0.05, Fisher exact test), markdirected behavior was significantly enhanced in the colored mark and mirror condition. doi:10.1371/journal.pbio.0060202.g003

had two tests in four different conditions. For each entry, the first value gives the number of mark-directed actions, while the second value gives the number of self-directed actions towards other parts of the body. Differences between conditions were analyzed by comparing the total frequencies from the first and second tests with the Fisher exact test. For Gerti, the score in the mirror and color condition differs from all other conditions: double asterisks (**) indicate p , 0.005. For Goldie, the score in the mirror and color condition differs from the no-mirror and color as well as from the nomirror and sham conditions: a single asterisk (*) indicates p , 0.05. The three instances with decimal numbers result from a slightly different rating by the two observers. For statistics, in these cases, numbers were rounded, and as such, they were conservative regarding the hypothesis.a Value missing due to loss of data during digitizing of video tapes; b Trial not completed. doi:10.1371/journal.pbio.0060202.t002

Figure 4 .
4Proportion of Self-Directed Behavior towards the Mark Area in Additional Tests (A) Proportion of mark-directed behavior by Gerti in a test session with change of marks in consecutive 5-min intervals. The color of each bar refers to the color of the mark used and subsequent 5-min periods of the test. Activity towards the mark was high for all colored marks, but low in the control condition (black mark). In all of the color conditions, the bird removed the mark. (B) Results from the first set of additional controls with a grid in front of the experimental cage instead of a Plexiglas wall. In the colored mark and mirror condition, mark-directed behavior was higher than in the colored mark and no-mirror condition (p , 0.02, Fisher exact test). doi:10.1371/journal.pbio.0060202.g004

Table 1 .
1Behavioral Data from Mirror Preference and Standardized Mirror ExplorationSubject
Test
Time with
View of Mirror
(min:sec)

Close
Inspection of
Mirror Image

Looks
Behind

Contingent
Behavior

Social
Behavior

Social Behavior
Later Test

Self-Directed
Mark Test

Self-Directed
Other

Gerti
1
19:17
19
5
2
0
No
þ
þ
2
19:24
23
5
4
0
3
18:21
10
2
4
0
4
17:12
11
0
1
0
5
9:26
7
1
0
0
Goldie
1
8:54
2
0
0
3
No
þ
þ
2
4:16

Table 2 .
2Frequencies of Self-Directed Behaviors in the Mark TestSubject
Test
Test with Two Trials in the
Four Different Conditions

No Mirror/
Color

No Mirror/
Sham

Mirror/
Color

Mirror/
Sham

Gerti
1st test
0/5
0/2
9/3
3/8.5
2nd test
1/4
1/8
5.5/1.5
1/5
Total
1/9
1/10
14.5/4.5**
4/13.5
Goldie
1st test
1/24
0/19
4/14
0/1
2nd test
0/0
-a
0/0
0/8
Total
1/24
0/19
4/14*
0/9
Harvey
1st test
-a
0/0
0/3
0/4
2nd test
-b
0/24.5
0/7
-b
Total
-
0/24.

Table 3 .Table 4 .
34Frequencies of Self-Directed Behaviors in the Mark Test Test with Change of Mark Within Session in the Subject Gerti Brain Weights, Body Weights, as Well as Percent Brainto-Body Weights of Some of the Different Species That Have Been Tested with MirrorsMirror/Yellow
Mirror/Blue
Mirror/Sham
Mirror/Red

2/4
4/3*
0/6
11/9*

This test with Gerti with change of mark within session consisted of four consecutive 5-
min periods. The asterisk (*) indicates difference from the mirror/sham condition, p ,
0.05.
doi:10.1371/journal.pbio.0060202.t003

Self-Recognition in Magpies
AcknowledgmentsAuthor contributions. HP and OG conceived and designed the experiments. HP and AS performed the experiments. HP, AS, and OG analyzed the data, contributed reagents/materials/analysis tools, and wrote the paper.Funding. The work was supported by grants from the Deutsche Forschungsgemeinschaft to HP (Pr 489/3-1) and to OG.Competing interests. The authors have declared that no competing interests exist.
Chimpanzees: self-recognition. G G GallupJr, Science. 167Gallup GG Jr (1970) Chimpanzees: self-recognition. Science 167: 86-87.

Untersuchungen zum Selbsterkennen im Spiegel bei Orang-Utans und einigen anderen Affenarten. J Lethmate, Dü, Z Tierpsychol. 33Lethmate J, Dü cker G (1973) Untersuchungen zum Selbsterkennen im Spiegel bei Orang-Utans und einigen anderen Affenarten. Z Tierpsychol 33: 248-269.

Reactions of a group of pygmy chimpanzees (Pan paniscus) to their mirror images: evidence of selfrecognition. V Walraven, L Van Elsacker, R Verheyen, Primates. 36Walraven V, van Elsacker L, Verheyen R (1995) Reactions of a group of pygmy chimpanzees (Pan paniscus) to their mirror images: evidence of self- recognition. Primates 36: 145-150.

Failure to demonstrate self-recognition in gorillas. D H Ledbetter, J A Basen, Am J Primatol. 2Ledbetter DH, Basen JA (1982) Failure to demonstrate self-recognition in gorillas. Am J Primatol 2: 307-310.

Responses of gibbons (Hylobates lar) to their mirror images. C W Hyatt, Am J Primatol. 45Hyatt CW (1998) Responses of gibbons (Hylobates lar) to their mirror images. Am J Primatol 45: 307-311.

Self-recognition and self-awareness in lowland gorillas. Fgp Patterson, R H Cohn, Self-awareness in animals and humans: developmental perspectives. Parker ST, Mitchell RWNew York (New YorkCambridge University PressPatterson FGP, Cohn RH (1994) Self-recognition and self-awareness in lowland gorillas. In: Parker ST, Mitchell RW, editors. Self-awareness in animals and humans: developmental perspectives. New York (New York): Cambridge University Press. pp. 273-290.

Observations on the behavior of gibbons (Hylobates leucogeny, H. gabriellae, and H. lar) in the presence of mirrors. M Ujhelyi, B Merker, P Buk, T Geissmann, J Comp Psychol. 114Ujhelyi M, Merker B, Buk P., Geissmann T (2000) Observations on the behavior of gibbons (Hylobates leucogeny, H. gabriellae, and H. lar) in the presence of mirrors. J Comp Psychol 114: 253-262.

Self-recognition in chimpanzees (Pan troglodytes): distribution, ontogeny, and patterns of emergence. D J Povinelli, A B Rulf, K R Landau, D T Bierschwale, J Comp Psychol. 107Povinelli DJ, Rulf AB, Landau KR, Bierschwale DT (1993) Self-recognition in chimpanzees (Pan troglodytes): distribution, ontogeny, and patterns of emergence. J Comp Psychol 107: 347-372.

Mirror self-recognition in the bottlenose dolphin: a case of cognitive convergence. D Reiss, L Marino, Proc Natl Acad Sci U S A. 98Reiss D, Marino L (2001) Mirror self-recognition in the bottlenose dolphin: a case of cognitive convergence. Proc Natl Acad Sci U S A 98: 5937-5942.

Self-recognition in an Asian elephant. J M Plotnik, Fbm De Waal, D Reiss, Proc Natl Acad Sci U S A. 103Plotnik JM, de Waal FBM, Reiss D (2006) Self-recognition in an Asian elephant. Proc Natl Acad Sci U S A 103: 17053-17057.

Effects of experience and social context on prospective caching strategies by scrub jays. M J Emery, N S Clayton, Nature. 414Emery MJ, Clayton NS (2001) Effects of experience and social context on prospective caching strategies by scrub jays. Nature 414: 443-446.

Personalized memories for food-hoards in Magpies. H Prior, N Gonzalez-Platta, Gü Ntü Rkü N O, Ravens Today: Third International Symposium on the Raven (Corvus corax. Metelen, GermanyPrior H, Gonzalez-Platta N, Gü ntü rkü n O (2004) Personalized memories for food-hoards in Magpies. Ravens Today: Third International Symposium on the Raven (Corvus corax).20-22 July 2004; Metelen, Germany.

Food-caching western scrub-jays keep track of who was watching when. J M Dally, N J Emery, N S Clayton, Science. 312Dally JM, Emery NJ, Clayton NS (2006). Food-caching western scrub-jays keep track of who was watching when. Science 312: 1662-1665.

Putting the altruism back into altruism: the evolution of empathy. Fbm De Waal, Annu Rev Psychol. 59De Waal FBM (2008). Putting the altruism back into altruism: the evolution of empathy. Annu Rev Psychol 59: 279-300.

Avian brains and a new understanding of vertebrate brain evolution. E D Jarvis, O Gü Ntü Rkü N, L Bruce, A Csillag, H Karten, Nat Rev Neurosci. 6Jarvis ED, Gü ntü rkü n O, Bruce L, Csillag A, Karten H, et al. (2005) Avian brains and a new understanding of vertebrate brain evolution. Nat Rev Neurosci 6: 151-159.

Quantitative development of brain and brain structures in birds (Galliformes and Passeriformes) compared to that in mammals (Insectivores and Primates). G Rehkä Mper, H D Frahm, K Zilles, Brain Behav Evol. 37Rehkä mper G, Frahm HD, Zilles K (1991) Quantitative development of brain and brain structures in birds (Galliformes and Passeriformes) compared to that in mammals (Insectivores and Primates). Brain Behav Evol 37: 125-143.

The mentality of crows: convergent evolution of intelligence in corvids and apes. N J Emery, N S Clayton, Science. 306Emery NJ, Clayton NS (2004) The mentality of crows: convergent evolution of intelligence in corvids and apes. Science 306: 1903-1907.

Animal behavior: laterality in tool manufacture by crows. G R Hunt, M C Corballis, R D Gray, Nature. 414707Hunt GR, Corballis MC, Gray RD (2001) Animal behavior: laterality in tool manufacture by crows. Nature 414: 707.

Shaping of hooks in New Caledonian crows. A A Weir, J Chappell, A Kacelnik, Science. 297981Weir AA, Chappell J, Kacelnik A (2002) Shaping of hooks in New Caledonian crows. Science 297: 981.

Episodic-like memory during cache recovery by scrub jays. N S Clayton, A Dickinson, Nature. 395Clayton NS, Dickinson A (1998) Episodic-like memory during cache recovery by scrub jays. Nature 395: 272-274.

Mirror use by African grey parrots (Psittacus erithacus). I M Pepperberg, S E Garcia, E C Jackson, S Marconi, J Comp Psychol. 109Pepperberg IM, Garcia SE, Jackson EC, Marconi S (1995) Mirror use by African grey parrots (Psittacus erithacus). J Comp Psychol 109: 189-195.

Development of object permanence in food-storing magpies (Pica pica). B Pollok, H Prior, Gü Ntü Rkü N O, J Comp Psychol. 114Pollok B, Prior H, Gü ntü rkü n O (2000) Development of object permanence in food-storing magpies (Pica pica). J Comp Psychol 114: 148-157.

Chimpanzees recognize themselves in mirrors. D J Povinelli, G G GallupJr, T J Eddy, D T Bierschwale, M C Engstrom, Anim Behav. 53Povinelli DJ, Gallup GG Jr, Eddy TJ, Bierschwale DT, Engstrom MC, et al. (1997) Chimpanzees recognize themselves in mirrors. Anim Behav 53: 1083-1088.

Preening and associated comfort behavior in birds. J D Delius, Ann N Y Acad Sci. 525Delius JD (1988) Preening and associated comfort behavior in birds. Ann N Y Acad Sci 525: 40-55.

Not all chimpanzees (Pan troglodytes) show selfrecognition. K B Swartz, S Evans, Primates. 32Swartz KB, Evans S (1991) Not all chimpanzees (Pan troglodytes) show self- recognition. Primates 32: 483-496.

Extraordinary large brains in tool-using New Caledonian crows (Corvus moneduloides). J Cnotka, G Gü Ntü Rkü N O, Rehkä Mper, R D Gray, G R Hunt, Neurosci Lett. 433Cnotka J, Gü ntü rkü n O, Rehkä mper G, Gray RD, Hunt GR (2008) Extraordinary large brains in tool-using New Caledonian crows (Corvus moneduloides). Neurosci Lett 433: 241-245.

Interspecific allometry of the brain and brain regions in parrots (Psittaciformes): comparisons with other birds and primates. A N Iwaniuk, K M Dean, J E Nelson, Brain Behav Evol. 65Iwaniuk AN, Dean KM, Nelson JE (2005) Interspecific allometry of the brain and brain regions in parrots (Psittaciformes): comparisons with other birds and primates. Brain Behav Evol 65: 40-59.

Self-awareness'' in the pigeon. R Epstein, R P Lanza, B F Skinner, Science. 212Epstein R, Lanza RP, Skinner BF (1981) ''Self-awareness'' in the pigeon. Science 212: 695-696.

Further reflections on mirror-usage by pigeons: lessons from Winnie the Pooh and Pinocchio too. Rkr Thompson, C L Contie, Self-awareness in animals and humans. Parker S, Boccia M, Mitchell RNew York (New YorkCambridge University PressThompson RKR, Contie CL (1994) Further reflections on mirror-usage by pigeons: lessons from Winnie the Pooh and Pinocchio too. In: Parker S, Boccia M, Mitchell R, editors. Self-awareness in animals and humans. New York (New York): Cambridge University Press. pp. 392-409.

Absence of self-recognition in a monkey (Macaca fascicularis) following prolonged exposure to a mirror. G G GallupJr, Dev Psychobiol. 10Gallup GG Jr (1977) Absence of self-recognition in a monkey (Macaca fascicularis) following prolonged exposure to a mirror. Dev Psychobiol 10: 281-284.

Social responding to mirrors in rhesus macaques (Macaca mulatta): Effects of changing mirror location. S D Suarez, G G GallupJr, Am J Primatol. 11Suarez SD, Gallup GG Jr (1986). Social responding to mirrors in rhesus macaques (Macaca mulatta): Effects of changing mirror location. Am J Primatol 11: 239-244.

Further reflections on self-recognition in primates. G G GallupJr, D J Povinelli, S D Suarez, J R Anderson, J Lethmate, Anim Behav. 50Gallup GG Jr, Povinelli DJ, Suarez SD, Anderson JR, Lethmate J, et al. (1995) Further reflections on self-recognition in primates. Anim Behav 50: 1525- 1532.

Reflections on self-recognition in primates. C M Heyes, Anim Behav. 47Heyes CM (1994) Reflections on self-recognition in primates. Anim Behav 47: 909-919.

Theory of mind in nonhuman primates. C M Heyes, Behav Brain Sci. 21Heyes CM (1998) Theory of mind in nonhuman primates. Behav Brain Sci 21: 101-114.

Monkeys, mirrors, mark tests, and minds. S M Platek, S L Levin, Trends Ecol Evol. 19Platek SM, Levin SL (2004) Monkeys, mirrors, mark tests, and minds. Trends Ecol Evol 19: 406-407.

The monkey in the mirror: hardly a stranger. Fbm De Waal, Proc Natl Acad Sci U S A. 102De Waal FBM (2005) The monkey in the mirror: hardly a stranger. Proc Natl Acad Sci U S A 102: 11140-11147.

Discrimination of moving video images of self by pigeons (Columba livia). K Toda, S Watanabe, doi:10.1007/ s10071-008-0161-4Anim Cogn. E-pub ahead of printToda K, Watanabe S (2008). Discrimination of moving video images of self by pigeons (Columba livia). Anim Cogn. E-pub ahead of print. doi:10.1007/ s10071-008-0161-4

Where in the brain is the self?. T E Feinberg, J E Keenan, Conscious Cogn. 14Feinberg TE, Keenan JE (2005) Where in the brain is the self? Conscious Cogn 14: 661-678.

Five levels of self-recognition as they unfold early in life. P Rochat, Conscious Cogn. 12Rochat P (2003) Five levels of self-recognition as they unfold early in life. Conscious Cogn 12: 717-731.

The avian 'prefrontal cortex' and cognition. Gü Ntü Rkü N O, Curr Opin Neurobiol. 15Gü ntü rkü n O (2005) The avian 'prefrontal cortex' and cognition. Curr Opin Neurobiol 15: 686-693.

Corvid cognition. N S Clayton, N J Emery, Curr Biol. 15Clayton NS, Emery NJ (2005) Corvid cognition. Curr Biol 15: R80-81.

Ravens, Corvus corax, differentiate between knowledgeable and ignorant competitors. T Bugnyar, B Heinrich, Proc Biol Sci. 272Bugnyar T, Heinrich B (2005) Ravens, Corvus corax, differentiate between knowledgeable and ignorant competitors. Proc Biol Sci 272: 1641-1646.

Evolution of the neural basis of consciousness: a bird-mammal comparison. A B Butler, P R Manger, Bib Lindahl, P Arhem, Bioessays. 27Butler AB, Manger PR, Lindahl BIB, Arhem P (2005) Evolution of the neural basis of consciousness: a bird-mammal comparison. Bioessays 27: 923-926.

Binocular visual field differences among various breeds of pigeons. H J Jahnke, Bird Behav. 5Jahnke HJ (1984) Binocular visual field differences among various breeds of pigeons. Bird Behav 5: 96-102.

The magpies: the ecology and behaviour of black-billed and yellow-billed magpies. T Birkhead, Poyser270LondonBirkhead T (1991) The magpies: the ecology and behaviour of black-billed and yellow-billed magpies. London: Poyser. 270 p.


An ontological exploration of change and constancy
12 Dec. 2013

Ananka Loubser firstname.lastname@example.com
School of Philosophy
North-West University
Potchefstroom CampusSouth Africa

Private Bag X6001
2520PotchefstroomSouth Africa

An ontological exploration of change and constancy
12 Dec. 2013F1F2E62A3CF1F2CF3684F91674A509C610.4102/koers.v78i2.2108Received: 11 Apr. 2013 Accepted: 28 Oct. 2013
1.I am referring to this group of philosophers as an example, but will not deal with them here.I have already mentioned them in other articles (Loubser in press, 2012).2.The numbering of the fragments is in accordance with the notation in Diels and Kranz (1959)(1960).

The history of philosophy presents a variety of viewpoints regarding the ontological primacy of either change or constancy.Some views regard change as foundational, to the point where constancy is denied (e.g.Heraclitus).Other views regard constancy as so important, that change becomes unthinkable (e.g.Parmenides).The apparent dialectical tension between the different conceptions demands an ontological clarification of these issues.This study illustrates and evaluates the relationship between change and constancy in the viewpoints of various philosophers and scientists throughout history.This is done by appropriating a reformational insight that change and constancy exist in cohesion.The study finds that the relationship between change and constancy is not dialectical, but rather one of integration, seated in irreducible primitive domains (modalities).The purpose of the article is twofold (1) to show that change and constancy cannot be reduced to one another but can only exist in a relationship of coherence and (2) to contribute a systematic clarification of framework change in terms of the relationship between change and onstancy on the ontological level.

Orientation

In epistemic frameworks, change and constancy occur according to a pattern.This pattern reflects the irreducibility of coherents (modalities), where change and constancy exist in cohesion.As a result, change can never be completely random or absolute.This central theoretical assumption underlies a research project discerning a level of consensus regarding the characteristics and functions of epistemic frameworks (Loubser 2013), as well as the factors shaping framework change and the relationship between these factors (Loubser in press).A further part of this project tries to achieve clarity on how framework changes occur (Loubser 2012).Framework changes can, for instance, be conceptualised as being either constrained, predictable and even predetermined or random, unpredictable and free from constraints.Some conceptions attempt a synthesis between the more radical positions.At an earlier phase of the research project the need for an ontological exploration of change and constancy and of substantiation of the main thesis (Loubser 2012) was announced.

In recent philosophy, some conceptions seem to regard change as foundational, to the point where change becomes the only constant. 1 The conceptions where change is everything and constancy denied can be traced from antiquity (Heraclitus Fr. 12, 49a) 2 and are also popular in 'n Ontologiese verkenning van verandering en konstantheid.Die geskiedenis van filosofie vertoon 'n verskeidenheid van standpunte aangaande die ontologiese voorrang van óf verandering óf konstantheid.Sommige beskouings aanvaar verandering as fundamenteel, tot die punt waar konstantheid ontken word (bv.Heraklitus).Ander beskouings aanvaar konstantheid as so belangrik, dat verandering ondenkbaar word (bv.Parmenides).Die oënskynlike dialektiese spanning tussen die verskillende konsepsies vereis 'n ontologiese uitklaring van die kwessies.Hierdie studie illustreer en evalueer die verhouding tussen verandering en konstantheid in die standpunte van verskeie wetenskapsfilosowe deur die geskiedenis.Dit word gedoen deur 'n reformatoriese insig aan te neem, naamlik dat verandering en konstantheid in 'n kohesie bestaan.Die studie vind dat die verhouding tussen verandering en konstantheid nie dialekties is nie, maar eerder een van integrasie, gesetel in onreduseerbare primitiewe domeine (modaliteite).Die doel van die artikel is tweeledig (1) om te toon dat verandering en konstantheid nie tot mekaar gereduseer kan word nie, maar in 'n verhouding van koherensie bestaan en (2) om 'n sistematiese uitklaring van raamwerkverandering, in terme van die verhouding tussen verandering en konstantheid op die ontologiese vlak, by te dra.

Scan this QR code with your smart phone or mobile device to read online.

Read online:

postmodernity.They do, however, harbour some problematic internal incoherence.In order for change to be recognised, some kind of constancy must be present (Strauss 2005:225) and the idea that change itself becomes the only constant is therefore rather paradoxical.Other conceptions regard constancy as fundamental to the point where change becomes unthinkable (Parmenides Fr. 2,6,7,8).The apparent dialectical tension between these different conceptions of change and constancy has its roots in antiquity and demands an ontological clarification of these issues.This brings us to the problem statement of the current article: What is the ontological relationship between change and constancy?

The present investigation proceeds by evaluating a few different ontological conceptions of the relationship between change and constancy in antiquity.Since the issue appears to be still problematic in philosophy, a few modern and postmodern conceptions are considered in addition to the more ancient examples.3This article does not attempt to provide a complete history of the idea, but merely shows that some problems do not die off easily and that some basic trends seem to repeat themselves.I will argue (with Strauss) for a position where change and constancy go hand in hand, because they are both rooted in primitive domains (modalities) which are irreducible.Change is based on the physical aspect of reality and constancy is rooted in the kinematic aspect (Strauss 2009:164-167).Should we relate this ontological principle to epistemic frameworks, it would appear that they do not change absolutely or arbitrarily, but rather have some kind of plasticity (Loubser 2012).

In the following sections I explore the relationship between change and constancy in Greek philosophy, whilst also paying some attention to the theme of unity and diversity in order to sketch a broader picture and to show how all these issues are interrelated.

Change and constancy in Antiquity

Thales

According to Allen (1966:1) every history of philosophy begins with Thales.This article happens to begin with the opinions of Thales as well, since his philosophy serves as the framework of beliefs which gave rise to ancient thought about the nature of change and constancy.

Thales's pronouncement that the source of all things is water means that (1) all things must have a source and (2) that this source is singular (i.e. one thing) (Allen 1966:1-2).From these two assumptions, it follows that: the universe is bound to a single principle, the primordial water, by a single relationship, that of derivation' and that 'nature is one whole, with unchanging ways of its own, to be accounted for in terms of a unitary principle of explanation.(Allen 1966:2) For Thales, therefore, the nature of the world is singular, holistic and constant.Although the primordial water was 'alive' and therefore 'capable of spontaneous movement', so that it becomes the 'source of movement' in the world (Allen 1966:2), Thales does not give an explanation of how this singular source could change to give rise to diversity in the world.The question about change was first posed by Anaximander: 'How is the qualitative diversity of the world to be reconciled with the primordial unity of its source?'

Anaximander

In order to address this question, Anaximander raises an important objection to Thales.For Thales, the primordial element is simultaneously unbounded and water.Water (the wet) stands in a relationship of opposition to other entities that embody the dry.If water were to be unbounded, its opposite would cease to exist (Allen 1966:2). 4  Anaximander proposes that the primordial principle (the Unbounded) is not to be associated with any sensible opposite, nor does it have any characteristics that can be found in the world of sensory experience.The Unbounded is internally undifferentiated (Allen 1966:2-3).Furthermore, Aristotle 5 interprets Anaximander's Boundless to be a mixture of all the sensible opposites (water, air, fire and earth) so that 'the opposites fuse in it' and 'it is itself of no determinate sort, a thing which is no kind because it is all kinds' (Allen 1966:3).According to Anaximander, the Nonlimited is 'everlasting and ageless' (Fr.2) as well as 'immortal and indestructible ' (Fr. 3;cf. Freeman 1971:19) and therefore it is constant.

Anaximander's answer to the question about change is that the different elements (or opposites) separate from the original material and that these opposing elements then 'war' upon one another (Fr. 1).This enmity between the opposites causes a pendulum dynamic (where one opposite, encroaching on the domain of the other, is turned into the other, and vice versa).This cycle is kept in balance by Time, so that the world is in equilibrium (Fr. 1;cf. Allen 1966:3).In this way, although constancy still prevails in his philosophy, Anaximander tries to account for change.

Anaximander is not the only philosopher to propose an answer to the question about change, and a different conception can be found in the thought of Anaximenes.

Anaximenes

For Anaximenes, the primordial unity is to be identified with a substance (air, mist or breath) and everything else is made out of this material (Fr.2).Diversity in the world occurs when this primary substance undergoes change of a quantitative nature.This means that qualitative diversity is dependent on the quantitative variation (thickening and thinning, 4.Anaximander's objection to Thales is reported by Aristotle Physics 204b 24.

condensation and rarefaction) of the primary substance (Allen 1966:4).According to Anaximenes, air (when made finer) becomes fire or (when made thicker) wind.When air is made thicker still, it progressively becomes cloud, water, then earth, stones and everything else (Freeman 1971:33).

Anaximenes believes, like Thales, that the primary substance is ensouled and this is the cause of motion in the world (Allen 1966:4).Interestingly, for Anaximenes, motion is eternal, but change comes about through it.The primary substance (air) is revealed by motion and is always in motion, for 'things that change do not change unless there be movement' (Freeman 1971:33-34).I will come back to change and constancy in relation to energy and movement later (see below), since it appears that in Modernity movement is associated with constancy rather than change.

Heraclitus

Like Anaximander, Heraclitus espouses a principle of isonomy that maintains balance in the world process.In the case of Heraclitus, this principle is called 'logos' and is identified with a sensible element, namely fire (Fr. 30;cf. Allen 1966:10).As the first principle of knowledge, the 'logos' has connotations of proportion, measure and pattern.For Heraclitus, however, the 'logos' also represents the first principle of existence: it is the 'unity of the world that sustains it as a process ' (Fr. 1;cf. Allen 1966:10).The 'logos' maintains the balance between diverse and conflicting opposites in 'strife'.This balance differs from the equilibrium brought about by Time in Anaximander.According to Allen (1966:10), Anaximander's Time produces equilibrium in a cyclical alteration of excess, whereas the 'logos' in Heraclitus maintains the balance at every given moment.Since the balance is continuous, the opposites being drawn apart are drawn back together at the same time and thus they are being maintained, constantly, in equal measures (Allen 1966:10). 6 This means that the world process, for Heraclitus, is a circle and that movement in any direction around the circle is continually balanced by movement in the opposite direction (i.e. the way up and the way down happen simultaneously: Fr. 60).The opposites, then, become in a sense the same (Fr. 88;cf. Allen 1966:10-11).Vollenhoven (2005a:35) emphasises the point further: the two processes do not follow one another, but rather happen simultaneously, so that the continuation in the world is a matter of 'the continual running into each other of two simultaneous streams'. 7In the first place, this type of thinking is contradictory.Because the world is self-contradictory, 'the knowledge that describes this world cannot acknowledge as norm principles that would exclude contradictions in thinking' (Vollenhoven 2005a:35).Secondly, because the origin of all things is eternally active fire, Heraclitus is a monist.This leads Vollenhoven (2005a:35;cf. 2005b:92) to describe Heraclitus's thought as a form of contradictory monism.

6.Heraclitus uses the metaphor of the bow (or lyre) to describe this back-stretched connection (Fr. 51;cf. Allen 1966:10).

7.For Vollenhoven (2005a:35), the term 'coincidentia oppositorum' [coincidence of opposites] is eminently suited to this concept.

Although the 'logos' itself is constant (Allen 1966:11), the emphasis in Heraclitus's world is very much on change (Fr.91).Both Plato and Aristotle describe this as the doctrine of perpetual flux where 'all things change and nothing remain at rest'. 8The first reaction against this doctrine is provided by Parmenides.

Parmenides

In Parmenides's view, the belief in the reality of the physical world (of plurality and change) is unsatisfactory and is to be substituted by the belief in One Being.The latter is unchanging, ungenerated, indestructible and spherical (Fr. 7, 8;cf. Allen 1966:12).His justification for belief in the One Being is demonstrated in the poem, Way of Truth, by reference to a disjunction, which can be reduced to 'It is or It is not'.The first disjunct is the 'way of true inquiry', whereas the second is the 'unthinkable, unknowable, not to be uttered'; and since thinking and being share the same ontological status (for Parmenides), the second disjunct is to be wholly rejected (Fr.2; cf.Allen 1966:11).

In contrast to the 'way of true inquiry', Parmenides (Fr. 6) also refers to the 'way of mortal opinion'.The latter presupposes the world of nature as having contents which 'come to be and cease to be' and thus can be reduced to: 'It is and is not'.For Parmenides, the 'way of mortal opinion' is also to be rejected, again on the grounds of the original disjunction (Fr. 8;cf. Allen 1966:12).This means that Parmenides draws a distinction between appearance and reality as well as between knowledge and opinion.In the end, plurality and change are rejected in favour of constancy.

It would appear as though, at the beginning of the fifth century, Greek opinions regarding the relationship between change and constancy are rather polarised.On the one hand, Heraclitus emphasises change, whereas, on the other, Parmenides argues that constancy has ontological primacy.It is not surprising, then, that the reaction to this situation included attempts to synthesise the two opposing positions.According to Allen (1966:14-15), the main challenge after Parmenides was to reconcile the sensible world (of plurality and change) with criteria for reality that it cannot satisfy.These criteria include that the world should be intelligible and therefore free from generation and destruction (i.e.change).

Empedocles: An attempt at integration?

The proposal from Empedocles rests on the notion that certain elements are constant (satisfying the criteria of reality) and that change occurs when these elements are rearranged (Allen 1966:14-15).Like Parmenides, Empedocles denies the possibility of generation and destruction and accepts the existence of a holistic 'Sphere of Being'.Contrary to Parmenides, however, Empedocles conceives the Sphere as full of sensible opposites (the hot, the cold, the wet and the dry).Change occurs when these constant qualities rearrange 8.See Heraclitus Fr. 12; Plato Cratylus 402a and Aristotle Physics 253b 9.

within the Sphere (Fr.17; cf.Allen 1966:15).The arrangement of the qualities occurs continually under the compulsion of the cosmic forces of Love and Strife.This means that the various compounds (complex substances of the world) come to be and pass away, but simultaneously the primary qualities constituting the substances remain the same (Fr.17; cf.Allen 1966:15).Vollenhoven, however, does not regard Empedocles's philosophy of change and constancy as an attempt at integration.He (2005aHe ( :35, 2005b:127-128) :127-128) classifies Empedocles as a dualist and a structuralist, 9 inclined to constancy (cf.Olthuis & De Graaff 1978:20-21).

Evaluation

The natural philosophers can broadly be divided into two groups.The first group proceeds from an original unity (monism).Duality and plurality are still recognised, but must be explained in terms of the original unity and are therefore seen as secondary (Vollenhoven 2005a:33).In this group, we may place, for instance, Thales, Anaximander, Anaximenes and Heraclitus.The second group begins with more than one origin (dualism).Here, two or more equally original (and correlative) causes need to come together in order to give a secondary explanation for unity (Vollenhoven 2005a:33).

Parmenides and Empedocles may be placed in this group.

Vollenhoven neatly distinguishes the issue of unity and multiplicity (monism and dualism) from the issue of change and constancy.In fact, both monists and dualists can be inclined to cosmogonic or structuralist thought.should grant that monists are more often inclined to cosmogonic philosophy, whilst dualists and pluralists are inclined to structuralism.The reason for this seems to be a search for 'balance' (Olthuis & De Graaff 1978:21-22).Yet there are monists who are structuralists and dualists who choose cosmogonic thinking.

With regard to the main problem statement of the article, ancient thought seems to be polarised into positions giving ontological primacy either: (1) to constancy or (2) to change.Between these two poles there also seems to exist a third position (3) attempting an integration of positions ( 1) and

(2).According to the classification of Vollenhoven (2005a:35), this does not amount to a true integration, and in his method he keeps using only two categories: structuralist and cosmogonic philosophies.

The members of group (1) include Thales, Anaximander, Anaximenes and Parmenides.For Thales, nature is constant and no explanation of how this singular substance could change is given.Anaximander regards the primary principle as everlasting and indestructible (and therefore as constant) and defines change as the 'separation' of different opposites from this original material.The primary substance for Anaximenes remains constant, so that change is only understood in terms of qualitative variation (thickening 9.Philosophers in a 'structuralist' mode of thinking tend to emphasise constancy, whereas philosophers in a 'geneticist' mode emphasise change, development and becoming (Olthuis & De Graaff 1978:20-21).

and thinning, condensation and rarefaction) of the primary substance.However, in Parmenides, group (1) acquires its most radical proponent.He rejects change for belief in the One Being, which is absolutely unchanging.

With regard to position of group (2), the thought of Heraclitus places the emphasis very much on change.For Heraclitus, the first principle ('logos') maintains a balance between diverse and conflicting opposites.This means that the world process is in continuous flux.

In the next section, we find the continuation of some of these issues in modernity and postmodernity.

Change and constancy in modernity and postmodernity

An introductory overview

In the previous section, we have seen various ancient conceptions giving ontological primacy to either change or constancy.Debates on these dilemmas seem to be perennial in the history of philosophy and, of course, continued through the Middle Ages.This article, however, forms part of a research project (Loubser 2012(Loubser , 2013, in press, in press) investigating more contemporary trends and does therefore not provide a complete historical overview.

Focusing on more recent examples, we again find conceptions emphasising change, to the point that it becomes the only constant (e.g. in Darwin, as well as some popular postmodern conceptions).Other conceptions may regard constancy as being fundamental to the point that change is denied.This can lead to positions that grant ontological primacy to constancy to the extent that change becomes unthinkable, for example in the viewpoints of Von Varga (1953:59-61).The apparent dialectical tension between the different conceptions of change and constancy has also given rise to contemporary attempts at finding 'patterns' in changes.One such example can be found in the work of Gerald Holton.

Holton (1978:8) finds elements (themata) that function to constrain, motivate, guide and even polarise scientific research and scientists.This means that there are constant themes in scientific concepts, methods, problems and hypotheses.Even though the themata function at an epistemological, rather than the ontological level, we can infer that they tell us something about the world through their importance in science.Moreover, Holton (1978:10) finds that the number of themata is limited (in fact, very small) with new themata being added only very rarely.This means that the themata are very persistent and that they fare very well in newly elaborated contexts.

In this project we have often dealt with work of philosophers of science.However, the work of some scientists themselves also seems to contain a polarised notion of either change, or constancy.In the next two sections, we look at examples in the legacies of Charles Darwin and Albert Einstein.

The importance of change in the work of Darwin

In his work On the origin of species, Charles Darwin (1869:92) defined 'natural selection' as the 'preservation of favorable variations, and the destruction of injurious variations'.According to Darwin (1869), variations that are inert would not be affected by natural selection but would be:

left as a fluctuating element, as perhaps we see in certain polymorphic species, or would ultimately become fixed, owing to the nature of the organism and the nature of the conditions.(p.92) Vollenhoven (2005b:96-97) regards Darwin as a monist and a geneticist.With regard to change and constancy, Darwin seems to hold that the natural (biological) world is inherently changeful 10 and that only the 'fittest' survive.This has led neo-Darwinism to regard the action of two phenomena, that of mutation and natural selection to occur in tandem (Strauss 2009:110).Since mutation normally occurs to the organism's detriment, only when the aforementioned phenomena act in tandem can the disadvantaged living entity emerge as the advantaged.

According to Strauss (2009:110-111), the role attributed to mutation and natural selection support the main thesis of neo-Darwinism, namely the assumption that the only reality within 'living' nature is change.Strauss (2009:110-111) criticises this assumption by stating that 'only when mutation and natural selection are operating as a constant (conditioning) law for the existence of living entities, is it possible to account for the changefulness of the latter'.His point is that the law-effect of mutation and natural selection is supposed to be constant and therefore not everything is changing in the bio-world.

It is not only in the world of biology where scientists think about change and constancy.In the next section we consider an example from the world of physics.

The importance of constancy in some physical theories

According to Strauss (2009:411), a proper elaboration of the insight that change presupposes constancy, can be found in Galileo's formulation of the law of inertia and in Einstein's theory of relativity.The core of Einstein's theory primarily emphasises constancy (of the velocity of light in a vacuum).This means that whatever is in motion moves relatively to an element of constancy (Strauss 2009:411).Furthermore, for Einstein, the distinction between the kinematic and physical aspects of reality is related to the difference between reversibility and irreversibility (Einstein 1959:43;cf. Strauss 2011:6-7).This enables Einstein to reject the viewpoint that all physical processes are reversible and thus reducible to mechanistic movement (Strauss 2011:7).Galileo's insights and formulation of the law of inertia is revisited below.Before then, it is time to consider the nature of change and 10.Strauss (2009:111, fn. 1) points out that this assumpti on greatly in� uences Darwin's Strauss (2009:111, fn. 1) points out that this assumption greatly in�uences Darwin's use of language.The terms 'constancy' (2) or 'persistence/persistently' (3) occur in a total of five instances in his work (Darwin 1869), whereas terms like 'change' (268), 'variation' (281) and 'variations' (162) occur much more frequently (number of occurrences indicated in brackets).

constancy as understood in the reformational tradition, in order to provide an alternative view that offers a valuable contribution towards solving the issue.

Attempts at integration: A reformational perspective

In the reformational tradition, two dimensions delimit what we can experience and therefore constitute the horizon of experience, namely modal aspects (so-called functions, aspects or modalities) and concrete (natural and social) entities (Strauss 2009:67).The dimensions cohere so that the modal aspects are 'universal, constant, functional frameworks at the basis of all entitary functioning and thus co-conditions the occurrence of all kinds of events' (Strauss 2009:67, 68-71).

Apart from the relationship between the two dimensions, the modal aspects themselves also cohere with one another.

In order to understand this inter-modal coherence, we must first explore the structure of the modal aspects.If change and constancy are respectively seated in two of the modal aspects, this line of argumentation can lead to demonstrating that change and constancy also cohere.This is done by proposing a synopsis of the views of Dooyeweerd, Strauss and Hart in which the eventual differences between them are neglected, in an attempt to show my own position.

The characteristics of modal aspects

In Dooyeweerd's (1979:40-41) ontology, created reality displays several modes (i.e.aspects or modalities) in the temporal order.Although the modes are irreducible to each other, they have analogical coherence.Dooyeweerd distinguishes between the numerical, spatial, kinematic, physical, biotic, psychical, logical, historical, lingual, social, economical, aesthetic, judicial, ethical and certitudinal modes of being.These modes of being can be understood as having the following characteristics:

1. Aspects have ontic status as universal functional modes of existence (belonging to a distinct dimension) and this means that aspects are neither functions nor properties of things (Hart 1984:198-201;Strauss 2006:64-69).

According to Hart (1984:85-134), modal aspects cohere with the dimension of entities without being 'dependent' upon those entities for their irreducible 'dimensional' existence.This means that the dimension of modal aspects co-determines the existence of entities (and events) in the sense that the latter invariably function within them.Furthermore, whenever entities or events function within a particular modal aspect, the unqualified universal meaning of the aspect requires a specification that is 'coloured' by the entity-structure of the entity function within the mode (Strauss 2009:143).2. The difference between aspects and entities implies that there are two distinct kinds of laws: (1) 'laws for aspects' (universal modal laws) and (2) 'laws for entities' (type laws) (Strauss 2009:25).In general, it can be said that modal laws hold for all possible classes of entity, whereas type laws hold for a limited class of entity only (Strauss 2009:79).

3. According to Dooyeweerd (1955:1:42-43), objective qualities that are ascribed to things in the logical and post-logical aspects are related to the subjective functions of human nature.They are related in such a way that the typical structure of the individuality of the thing (which is characterised by a specific relationship to its qualifying function) finds expression.Dooyeweerd (1955:1:43) uses the example of a bird's nest (characterised by a specific relation to animal life), which remains a bird's nest with respect to its objective logical characteristics and even if it is a possible object of human culture, symbolic signification, or aesthetic appreciation (Hart 1984:221-242).4. As a result of (3), we can distinguish between the norm side and the factual side within each aspect of reality (Strauss 2009:76).5.The factual side of aspects comprises the subject-subject and subject-object relationships, although the first aspect is an exception to this, since it has only subject-subject relationships (Strauss 2009:76-77).6.Every modal aspect is fitted into a cosmic time order (Hart 1984:149ff.), whilst bringing to expression (in its own modal structure) a functionally 'coloured' manifestation of 'cosmic time'.On the law side, it expresses itself as time order and on the factual side as time duration (Strauss 2009:77).The duration remains constantly subjected to the time order, so that, for example, in the aspect of organic life, one finds the temporal order of birth, maturing, adulthood, ageing and dying in most higher organisms (Dooyeweerd 1955:1:28).7.Each modal aspect has a core meaning (designated as its meaning nucleus or meaning kernel), which makes the modal aspect irreducible, indefinable and irreplaceable, since it founds the sphere sovereignty of every aspect (Strauss 2009:74-75).For Dooyeweerd (1979:43) this principle of sphere sovereignty is a creational principle connected with the scriptural ground motive of the Christian religion.

The above characteristics help us to understand the diversity between the aspects.According to Dooyeweerd (1955:2:74) full justice ought to be done to the specific sphere-sovereignty of the modal law-spheres, because each of the law-spheres is a temporal, modal refraction of the religious fullness of meaning.This means that every aspect accesses the whole of temporal coherence of meaning in its own modal structure.However, although the aspects are diverse, they also cohere with one another (Hart 1984:164).In the next section, we will see how this is possible.

The interrelatedness of modal aspects

The coherence between the modal aspects can be explained as follows:

1. Aspects are analogically related through moments of coherence with other aspects reflected within the structure of the particular aspect (Strauss 2009:75;Hart 1984:162-163).This means that the meaning of an aspect comes into expression only in this coherence.This feature is called the sphere universality of each aspect (Strauss 2009:76).

2. There is an order of succession amongst the modal aspects (Hart 1984:190-198).This means that 'the modal aspects are fitted into a cosmic order such that some are foundational to others' (Strauss 2009:170).For example, 11 both the numerical and the spatial aspects are presupposed within the structure of the kinematic aspect (2009:163).Hart (1984:151) designates the direction going through the modal order from lower to higher modes as the founding direction of the order.Here the lower level functions in a foundational way as support for the existence of the higher levels.In contrast, the developmental direction refers to the order in which lower functioning is enriched as a result of its being made serviceable to a higher order (Hart 1984:152).3. The moments of coherence between the modal aspects are referred to as analogies, 12 which embrace both retrocipations (backwards pointing towards coherence between an aspect and earlier aspects in the cosmic order of time) and anticipations (forward-pointing coherence towards aspects later in the order) (Strauss 2009:75).4. Furthermore, regarding the relationship between the sphere sovereignty (diversity) and sphere universality (coherence) of the aspects, Dooyeweerd maintains the following: 5. Sphere sovereignty can be maintained within the temporal inter-modal coherence of the different aspects only if the modal meaning of each law-sphere has a structure: law-spheres must have a nucleus guaranteeing the sphere sovereignty of the entire aspect.This nucleus must be surrounded by a number of analogical modal moments which partly refer backwards to the nuclei of other aspects and partly refer forward to aspects that are later in the cosmic arrangement (Dooyeweerd 1955:2:75;cf. Hart 1984:162).

In order to understand the significance of the theory of modal aspects for the ontological relationship between change and constancy, we first have to determine where the latter (respectively) are seated in the modal aspects.This is investigated in the next section.

Change and constancy as modal kernels of meaning

In defining the meaning nucleus of the kinematic aspect, Strauss (2009:89) once more refers to Galileo's experimental derivation of the law of inertia.The experiment rests on the hypothesis that whatever moves will continue its movement endlessly.This means that, whereas uniform motion does not need a cause, a change of motion requires an energyinput (physical cause) for both acceleration and deceleration.According to Strauss (2009:89), movement is something original in a functional sense and our immediate experiential awareness of uniform motion captures the meaning of 11.According to Strauss (2009:163), Galileo used a thought experiment in 1638 in According to Strauss (2009:163), Galileo used a thought experiment in 1638 in which he contemplated the movement of a body on a path extended into infinity.I agree with Strauss that here the terms 'path' and 'extended' designate the spatial foundation of the kinematic aspect, whereas the term 'infinity' captures its numerical foundation.

12.Concrete examples of this can be found in composite expressions such as emoti onal Concrete examples of this can be found in composite expressions such as emotional strength (sensitive and physical aspects), economic trust (economic and certitudinal aspects) and aesthetic expression (aesthetic and lingual modes).

movement as constancy.Therefore, we may adopt the synonym constancy when designating the meaning nucleus of the kinematic aspect.

When it comes to the term change, however, we need to look to the physical aspect of reality.According to Strauss (2009:89) energy in all its forms always causes physical changes.This means that energy-operation (the nucleus of the physical aspect) entails the cause-effect relationship and forms the basis of causality in its original sense.Cause and effect always implies change.Terms like 'change' or 'dynamics', inasmuch as they are synonyms, may then be used to designate the nuclear meaning of the physical mode.

Change and constancy are interrelated

In the previous section we saw that constancy is seated in the kinematic aspect, whereas change belongs to the physical aspect of reality.Since the kinematic and physical aspects are interrelated, it follows that constancy and change cohere as well.

The reason for this coherence is that change can be established only on the basis of something persistent and constant (Strauss 2009:13).Without an awareness of persistence, the very notion of change becomes problematic in the sense of the question (Strauss 2009:165): What is it that undergoes change?Here, it may be helpful to refer back to point (1) above: the meaning of an aspect (or its nucleus, for example, change) only comes into expression in the coherence with other aspects (or their nuclei, in this case constancy) reflected within the structure of a particular aspect (the physical, in our current case).

To make the case more concrete, we may borrow yet another example from Strauss (2009):

Suppose an ageing person claims that she has changed a lot during the past two decades.This statement only has meaning on the basis of an implicit awareness of persistence, for there is a constant reference to the same person.The relationship between change and constancy is therefore an example of the 'coherence of irreducibles.(p.13)

Acknowledging the coherence of irreducibles between the kinematic and the physical aspects, opens up a new perspective in which constancy and change are no longer considered 'opposites' (Strauss 2009:166).An example from the natural sciences demonstrates the perspective.Let us consider the following statements:

1.The law of inertia assumes the constancy of motion if no physical forces interact with the movement under consideration.2. The discovery of irreversible physical processes (e.g.radioactive decay) confirms the distinct and irreducible meaning of the physical aspect.3.There exists an inter-modal connection between the kinematic and the physical aspects.4. Should the above statements be true, there seems to exist an analogical moment within the physical aspect, which reminds us of the functional meaning of the kinematic aspect.This makes it possible to arrive at a more precise description of the law of energy conservation: we find an analogy of the kinematic aspect on the law side of the physical aspect (Strauss 2009:319).

Conclusion

An investigation of and a comparison between different philosophical traditions giving ontological primacy to change or constancy, shows that these conceptions cannot be regarded as satisfactory.Rather, change and constancy are coherent, irreducible dimensions of reality and therefore basic (primitive) ontological categories.Change refers to the physical aspect of reality, whereas constancy refers to the kinematic aspect.These two aspects cannot be reduced to each other, but can exist only in a relationship of coherence.This means that in epistemic frameworks, change and constancy go hand in hand, pointing towards the idea of plasticity.This can shed light on the discussions in previous articles, in particular in Loubser (2012), where a clarification of this topic was announced, to illustrate better what was argued in that context.
 .The most important philosophers and scientists who debated these issues are included. Of course there are other important philosophers of science, but they are discussed elsewhere(Loubser in press, 2012).
AcknowledgementsCompeting interestsThe author declares that she has no financial or personal relationship(s) that may have inappropriately influenced her in writing this article.
Greek philosophy: Thales to Aristotle. R E Allen, 1966The Free PressNew York

The basic works of Aristotle. Aristotle, ' Physics, Transl R P Hardie, R K Gaye, R. McKeonRandom HouseNew York

On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. C Darwin, 1869John MurrayLondon

Die fragmente der Vorsokratiker, vols. I-III. H Diels, W Kranz, 1959-1960Weidmannsche VerlagbuchhandlungBerlin

A new critique of theoretical thought, vols I-IV, transl. H Dooyeweerd, D.H. Freeman & W. Young, Uitgeverij H.J. Paris1955Amsterdam

The roots of western culture: Pagan, secular and Christian options. H Dooyeweerd, 1979Wedge Publishing FoundationToronto

Autobiographical notes. A Einstein, Albert Einstein, philosopher-scientist. P A Schilpp, New YorkHarper Torchbooks1959

Ancilla to the pre-Socratic philosophers: A complete translation of the Fragments in Diels Fragmente der Vorsokratiker. K Freeman, 1971Basil Blackwell, Oxford

Understanding our world: An integral ontology. H Hart, 1984University Press of AmericaLanham

The scientific imagination: Case studies. G Holton, 1978Cambridge University PressCambridge

Changes in epistemic frameworks: Random or constrained?. R A Loubser, 10.4102/koers.v77i2.425Koers -Bulletin for Christian Scholarship. 7722012

Tracing some consensus on the nature of pre-scientific frameworks in philosophy of science. R A Loubser, Acta Academica. 4522013

Factors shaping scientific framework change'. R A Loubser, in press

J H Olthuis, A H De Graaff, Models of man in theology and psychology: Study guide, Institute for Christian studies. Toronto1978

Plato, ' Cratylus, Transl C D C Reeve, Plato: Complete works. J M Cooper, D S Hutchinson, IndianapolisHackett Publishing Company

Relativity and relativism: Historical and systematic considerations. D F M Strauss, Acta Academica. 3722005

The best known but least understood part of Dooyeweerd's philosophy. D F M Strauss, Tydskrif vir Christelike Wetenskap. 421/22006

Philosophy: Discipline of the disciplines. D F M Strauss, 2009Paideia PressGrand Rapids

Relasiebegrippe in die lig van die vraag oor of Einstein in die eerste plek 'n "relatiwiteitsteorie" ontwikkel het. D F M Strauss, 10.4102/satnt.v30i1.28Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie. 3012011Relation concepts in view of the question if Einstein in the first place developed a "theory of relativity

The problem-historical method and the history of philosophy. D H Vollenhoven, Th, K.A. Bril (ed.), transl. J. De Kievit, S. Francke, J.G. Friesen & R. Sweetman2005aDe Zaak HaesAmstelveen

. D H Vollenhoven, Th, Wijsgerig woordenboek, K.A. Bril2005bDe Zaak HaesAmstelveen

Einfuhrung in die erkenntnislehre: Die grundrichtungen und die grenzen der erkenntnis der wahrheit. Von Varga, 1953Ernst Reinhardt VerlagMünchen/Basel