## 1. Life and Works



Ludwik Fleck was born on July 11, 1896, in Lvov (now Lviv), at that
time under the rule of Austria-Hungary, to a family of Jewish
craftsman. His medical studies at the John Casimir University were
interrupted by military service. He graduated in 1922, when Lvov
belonged to the reborn Poland. At the end of his studies he was an
assistant of the famous typhus specialist Rudolf Weigl. In 1923 Fleck
founded a private laboratory of medical analysis and was in charge of
the Lvov Sick Fund and the bacteriological-chemical laboratories of
the General Public Hospital.



Although he was only loosely related with any academic environment at
that time, Fleck conducted medical research, the results of which he
published in about 40 papers, mostly in Polish and in German. In 1927
he published in Polish his first work in the philosophy of medicine:
"Some Specific Features of the Medical Way of Thinking".
Two years later he published in German a paper "On the Crisis of
'Reality'"(1929) inspired mostly by the quantum
revolution in physics. Both articles are of a provisional character,
but the first one already includes the terms "thought
style" and "incommensurability".



In September 1933 Fleck sent the manuscript of his book *Die
Analyse einer wissenschaftlichen Tatsache* to Moritz Schlick. In
March 1934, Schlick replied and expressed his willingness to recommend
it for publication under the condition that a specialist on the
history of medicine would also review it positively. In 1935, Benno
Schwabe finally published the book *Entstehung und Entwicklung
einer wissenschaftlichen Tatsache: Einfuhrung in die Lehre vom
Denkstil und Denkkollektiv* (The Genesis and Development of a
Scientific Fact: An Introduction to the Theory of Thought Style and
Thought Collective). It was accompanied by a Polish summary of the
main theses of the book (1934) and two important papers:
"Scientific Observation and Perception in General" (1935b)
and "The Problem of Epistemology" (1936). In Poland the
book was criticized by Izydora Dambska and Fleck answered her
critique in (1938). Fleck's next Polish philosophical article
(1939a) referred, among others, to a book by a psychiatrist and
historian of medicine, Tadeusz Bilikiewicz. Bilikiewicz replied with a
moderate critique of Fleck's epistemology. Fleck in turn wrote a
paper "Rejoinder to the Comments of Tadeusz Bilikiewicz"
(1939b) in which he stated strong anti-realistic theses. 



When Lvov was incorporated into the Ukrainian Soviet Republic in 1939,
Fleck had been appointed the head of the municipal laboratory of
hygiene and bacteriology. On June 30, 1941, Lvov was captured by
Germans. Anti-Jewish pogroms began, and Germans also started to murder
university professors of Polish origin. Fleck and his wife survived,
probably because Rudolf Weigl included him on the list of employees of
the Lvov Institute of Research on Typhus and Viruses. In August 1941,
Germans resettled Fleck to the Lvov ghetto, where he developed and
produced an anti-typhus vaccine from the urine of sick people. He was
then relocated with his family to the area of the pharmaceutical
company Laokoon and tasked with producing an anti-typhus vaccine for
German soldiers. Finally he and his wife and son were deported to the
concentration camp in Auschwitz. At first he was forced to do physical
labor, but later he was transferred to the camp's hospital with
the assignment to conduct bacteriological tests on prisoners. In
December 1943 Fleck was transferred to the concentration camp in
Buchenwald. There a group of prisoners--scientists and medical
doctors of various nationalities--led by a scientifically
illiterate German doctor produced an anti-typhus vaccine.



The Buchenwald concentration camp was liberated in April 1945. One
month later Fleck found his wife and son in Lvov, which once again
belonged to the Soviet Union. They hastily left for Poland, whose
territory--by the decision of the Allies--was moved 200 km
to the west. The Communist government in Poland was establishing Maria
Curie-Sklodowska University in Lublin, and since Germans murdered
many Polish scholars, there was a scarcity of employable professors.
In October 1945 Fleck became the head of the Institute of Medical
Microbiology at that university, and he became a full professor in
1950. In 1948 he testified in the Nuremberg Trials of German doctors,
who conducted criminal experiments on prisoners of concentration
camps.



He published two more epistemological papers in Polish:
"Problems of the Science of Science" (1946) and "To
Look, To See, To Know" (1947). Those texts do not add anything
important to the theory which he formulated in the 1930s. He was
absorbed by research on a defence mechanism which he discovered in
1942 and named "leucergy". It was the chief subject of
most of his roughly 80 medical papers which he published in those
years, mostly in Polish, but also in English and French. In 1952 he
became the director of the bacteriology and immunology laboratory of
the Institute of Mother and Child in Warsaw. Fleck was honored with
many high national distinctions; he had a company car at his disposal,
and attended international conferences abroad. In 1954 he became a
member of the Polish Academy of Sciences. 



When Fleck emigrated with his wife to Israel in 1957, where his only
son had been living for many years, he was already very ill with
cancer and heart problems. For a few years he was employed in the
Institute of Biological Research in Ness Ziona. He then wrote in
English his last philosophical paper "Crisis in Science. Towards
a Free and More Human Science", that was rejected by several
philosophical journals. Ludwik Fleck died on June 5, 1961, of a second
heart attack.


## 2. Predecessors



In his epistemological works, Fleck combined: (1) experience of a
scientist; (2) reflections on the history of medicine; (3)
philosophical ideas; and (4) sociological ideas. In the light of his
own sociology and philosophy of science, one needs first to ask which
thought collectives he belonged to and what thought styles he
assimilated.



(1) While working in a private laboratory and hospital Fleck conducted
certain medical research, but he remained outside university circles,
and his research was rather marginal.



(2) In the interwar period Poland was probably the only country where
faculties of medicine had chairs for the philosophy and history of
medicine (Lowy 1990). Between 1908 and 1919 Wladyslaw
Szumowski taught the history of medicine in Lvov. Fleck also had some
professional contact with two philosophers and historians of medicine,
Wlodzimierz Sieradzki and Witold Ziembicki. He was a friend of
Jakob Frostig, a philosophizing psychiatrist. It is worth
mentioning a few remarks from Frostig's *Das schizophrene
Denken. Phanomenologische Studien zum Problem der widersinnigen
Satze* (Leipzig 1929), which can be seen almost without any
change among those written by Fleck: "We mean by [the expression
'social group'] any group of people bound together by a
common 'intention'. Thus the group of mathematicians is a
group of a very special, mathematical mentality. (...) one and
the same person can (...) belong to several very different human
groups. (...) the group's collective storehouse ever
changes and with it the criteria for truth. (...) It is only in
relation to the collective stores of the group in question that we can
denote a state of affairs as correct or as a personal error"
(following Schnelle 1986, p. 9). However, Fleck does not mention any
of these scholars in his writings, even though they created the
thought style and intellectual mood that, according to his views, were
necessary for his sociology and philosophy of science to emerge. 



(3) Before World War II, Lvov had a "philosophical branch"
of a distinguished mathematical-philosophical school--the
Lvov-Warsaw School. Despite the fact that Fleck had connections with
this school, he never mentioned either Kazimierz Ajdukiewicz or Leon
Chwistek, even though Chwistek's idea of the multiplicity of
reality (in art but also in life and science) has much in common with
his theory of thought styles. In his writings Fleck makes a few
critical remarks on conventionalists and logical empiricists; however,
nothing really supports the claim that he knew their views well. Also,
Fleck's remarks on epistemology of Kant, Mach, Wundt and
Uexkull's are superficial and dispersed--he does not
adopt views from them, but only looks for some superficial
confirmation of his own claims. Thus, we cannot include Fleck among
any esoteric philosophical circles.



(4) In (1935a) Fleck devotes only a few pages to the sociology of
knowledge, and, moreover, he refers exclusively to the German
translation of Lucien Levy-Bruhl's book *Das Denken der
Naturvolker*, 1921 and to Wilhelm Jerusalem's paper of
1929. Clearly he did not know works of the "founders of
sociology of knowledge": Max Scheler and Karl Mannheim. Schnelle
(1986) even claims that Fleck had acquired the basic information on
the sociology of science from a popular paper published in Polish by
Pawel Rybicki. When Fleck mentions the works of Durkheim, Levy
Bruhl, Jerusalem or Gumplowicz, he does this superficially; he does
not adopt any of their conceptions and is content with a general
thesis that "What actually thinks within a person is not the
individual himself but his social community" (Gumplowicz; quot.
from Fleck 1935a, SS II.4). Fleck accuses them of ignoring the
results of their research into the beliefs of traditional societies
once they turn to scientific thinking, where they hold that
"perceptions proper" displace mythical elements, and a
traditional conviction on the existence of spirits and daemons is
replaced with justified beliefs about "what physically is
possible or impossible" (Levy-Bruhl, quot. from Fleck 1935a,
SS II.4). In contrast, Fleck claims that scientific thinking is an
object of sociological examination to the same extent as mythical
thinking.



An interesting hypothesis was recently formulated by Eva Hedfors
(2006), who critically evaluated Fleck's competencies in the
history of medicine. She claims that the chief role in the development
of his thought was played by the interdisciplinary journal *Die
Naturwissenschaften*, where on the turn of the 1920s and 1930s
scientists and philosophers carried out a philosophical debate about
the relativistic and quantum revolution in physics. According to
Hedfors this debate inspired Fleck, who wrote on the "physics of
tomorrow":



> 
> At the present time we are so fortunate as to witness the spectacle of
> the birth, the creation, of a new style of thinking. (...) Sooner
> or later much will change: the law of causality, the concepts of
> objectivity and subjectivity. Something else will be demanded from
> scientific solutions and different problems will be regarded as
> important. Much that has been proven will be found unproven, and much
> of what was never proven will turn out to be superfluous (Fleck 1929).
> 



As Fleck--because of the lack of education in this
area--could not write about physics, he found corresponding
episodes in the history of medicine with which he illustrated theses
circulating in the thought collective of physicists who were debating
what was happening in their discipline.


## 3. Thought Collectives



Immanuel Kant made us aware that while we learn about nature from
experience, in order to do this we have to know something before
experiencing anything. According to Kant, *a priori* synthetic
knowledge is unchangeable and plays an active role in cognition: our
picture of the world is formed as much by things in themselves as by
our forms of perception and categories of thought, and we will never
know whether and how that picture is similar to what exists
independently of our cognitive acts. Fleck adopted Kant's thesis
on the active role of cognitive *a priori*: an empty mind would
neither perceive nor think. So, before a mind starts to experience,
and on the basis of experience starts to think, it has to be filled
with some initial knowledge. But the quantum revolution in physics has
shown that there is nothing necessary or unchangeable in *a
priori* forms and categories. A non-Kantian explanation of the
origins of cognitive *a priori* was badly needed.



According to Fleck, the basic phenomenon we have to accept in order to
build the edifice of epistemology is the collective mental
differentiation of men (1936, II). People perceive and think
differently, but those differences concern groups rather than
individuals. So we speak of various ways of perceiving and thinking
about stars and planets by astronomers, by astrologists, by
theologians or by mystics. Those people understand each other very
well within their groups: an astronomer understands another astronomer
well, and an astrologist another astrologist; but between
groups--like between an astrologist and an astronomer--there
is usually no understanding.



Cognition is a collective activity. It is confusing just to say that
an individual X got to know a phenomenon P: one should say that
"X got to know P in the thought style S from the epoch E"
(1936, V)--yet the thought style S from the epoch E is a product
of a certain thought collective to which X belongs. What to a stubborn
metaphysician appears as necessary forms of thinking results from the
social nature of cognition:



> 
> A truly isolated investigator is impossible (...). An isolated
> investigator without bias and tradition, without forces of mental
> society acting upon him, and without the effect of the evolution of
> that society, would be blind and thoughtless. Thinking is a collective
> activity (...). Its product is a certain picture, which is
> visible only to anybody who takes part in this social activity, or a
> thought which is also clear to the members of the collective only.
> What we do think and how we do see depends on the thought-collective
> to which we belong (1935b).
> 



*A thought collective* is defined by Fleck as a community of
persons mutually exchanging ideas or maintaining intellectual
interaction (1935a, II.4). Members of that collective not only adopt
certain ways of perceiving and thinking, but they also continually
transform it--and this transformation does occur not so much
"in their heads" as in their interpersonal space. It is
easy to observe this phenomenon in everyday life. When a group of
people speak about something important, they start to speak about
things which would not cross their minds if they were alone and which
they would not tell if they were in another group of people. There
arises *a thought style* characteristic for that group. There
also arises a certain *collective mood* which straightens up
the ties among the group members and inclines them to act in a certain
way.



Some collectives last shortly--even only as long as an individual
conversation lasts. When social forces connecting people operate for a
long time, there arise thought collectives lasting for many
generations. They take forms of religious movements, folk traditions,
art or science. Long-lasting collectives create social institutions
which enable and regulate the method by which next generations are
added to a given collective: educational systems and social rituals
accompanying the admission of new members.



All members of small ethnic groups belong to the same thought
collective: everybody perceives and thinks in the same way, just like
everybody performs the same or very similar actions. Within more
developed societies there are many various collectives: religious,
artistic, scientific, astrological, and those related to fashion,
politics, economy, medicine, quack, sport, etc. When a thought style,
developed and employed by a collective, becomes sufficiently
sophisticated, the collective breaks into a small *esoteric
circle*--a group of specialists which "are in the
know"--and a wide *exoteric circle* for all those
members, who are under the influence of the style, but do not play an
active role in its formation. Members of the first group are those
"initiated"--priests and theologians in the case of
religion; artists and art critics in the case of art; scientists in
the case of science etc. The corresponding exoteric circles for those
groups are: lay believers; art-lovers; school teachers of physics,
chemistry, and biology, and also engineers and all people interested
in science.



Exoteric circles have an access to a proper thought style only through
esoteric circles--for example through listening to sermons given
by priests, or reading popular literature written by scientists.
Members of exoteric circles trust the initiated. But specialists and
members of esoteric circles are not independent of exoteric circles:
this is the "public opinion" which justifies the efforts
of specialists and gives them a stimulus to continue their work.



In contemporary societies almost everybody belongs to many thought
collectives; e.g. a scientist may be also a member of a certain
church, political party, mountain climbing club. An individual usually
belongs to distant thought collectives, so that conflicts between
thought styles coexisting in him/her do not arise. Most of people
belong only to exoteric circles; only few become members of any
esoteric circle, sporadically belonging to more than one. Everybody
also belongs to a wide "everyday life" collective (which
also differs from culture to culture).



Within the esoteric circle Fleck distinguishes the following
subgroups: (1) vanguard, "the group of scientists working
practically on a given problem", (2) the main body, "the
official community", and (3) the group of stragglers (1935a,
IV,4). In other places he omits stragglers and introduces a
distinction between professionals (specialists *sensu stricto*)
and more general specialists (1936, VI).


## 4. Collective Moods



Members of a thought collective naturally possess a certain bond, some
feeling of group solidarity, of being a "comrade",
"coreligionist", "countryman", or
"colleague". It is accompanied by the feeling of hostility
or contempt to a "stranger", who worships other gods, is
guided by other values, or uses unfamiliar words etc.



> 
> The force which maintains the collective and unites its members is
> derived from the community of the *collective mood*. This mood
> produces the readiness for an identically directed perception,
> evaluation and use of what is perceived, i.e. a common thought-style
> (1936, V).
> 



These are collective moods which induce members of collectives both to
sacrifice themselves for others and to burn dissenters at stakes. They
make scientists work for public enlightenment, and at the same time
they arouse the feeling of disdain for astrologists or alchemists.



Fleck stresses that there is no thinking which is free from emotions:
"There is only agreement or difference between feelings, and the
uniform agreement in the emotions of a society is, in its content,
called freedom from emotions" (1935a, II.4). Emotions have a
social character; they are already hidden in a language employed by a
collective. Technical terms not only denote something determined by
their definitions, but they also encompass "a certain specific
power, being not only a name but also a slogan", they have
"a specific thought-charm". This is why once the members
of an esoteric circle master technical terminology there appears a
sense of mission, and joining such a circle itself has "the
value of the sacrament of initiation" (1936, V).



If the position of an elite is stronger than the position of the
masses, the elite isolates itself and demands obedience from the
masses. Such collectives develop dogmatic styles of thinking in which
a test of correctness is usually located in some distant past in a
more or less mythical master or savior. Collective life acquires a
ceremonial character and access to the esoteric circle is
well-guarded. Conservatism reigns: there is no place for fundamentally
new ideas, and one can only better or worse realize the revealed
principles. This is characteristic of most religious collectives.



If the position of the masses is stronger than that of an
elite--like in scientific collectives--the elite endeavors
after trust and appreciation of the masses, pledging its commitment to
serve common good. This collective has a democratic character: the
test of correctness is "the recognition by everybody".
Everybody is encouraged to learn, and everybody who meets intellectual
standards can become a member of the esoteric circle. "This
obligation is also expressed in the democratically equal regard for
anybody that acquires knowledge. All research workers, as a matter of
principle, are regarded as possessing equal rights" (1935a,
IV.5). In principle every man--not only an elite with special
privileges--should be able to verify whether a statement is true,
to repeat an experiment conducted by somebody else etc.



Here an unsolvable problem arises. General education, necessary for
joining a scientific collective, is acquired in schools before
maturing, and if this is not achieved an individual is practically
doomed to remain outside the scientific collective. In science no
transfers from the uneducated general public to the body of general
specialists occur. However, a democratic respect for an (imagined)
"anybody" grants scientific thought styles an impersonal
character which in turn leads to the objectivization of collectively
created thought structures. Objective truth expressed clearly and
precisely becomes an ideal. Of course, this ideal is to be realized in
some distant (maybe even infinite) future. However, even if a
researcher herself is removed from the results of her work, a cult of
scientific heroes and geniuses devoted to scientific service
develops.



Part of a collective mood arises at the point of contact between
esoteric and exoteric circles. On the one hand, members of exoteric
circles usually trust professionals and they admire them. On the other
hand esoteric circles act under pressure of expectations of the
masses. When a certain domain lacks support from outside, it does not
have significant achievements. Fleck here uses an analogy of sand
carried by the wind. A rock sometimes hits its target and sometimes it
does not, whereas sand carried by the wind unavoidably accumulates in
hollows (1935a, III). So when some social pressure makes enough
researchers work long enough on a certain issue and obtain sufficient
material support, they finally arrive at more or less satisfying
results. A condition of success is not the alleged truth of employed
theories but the systematicity of research.


## 5. Genesis and Development of a Thought Style and of Facts



The democratically equal regard for everybody makes scientists write
popular works to familiarize laypersons--as far as it is
possible--with a current state of knowledge. They use widely
understood common language full of imprecise expressions and
metaphors. Since popular texts cannot include complications which a
professional meets every day in her work and because an author speaks
to the public as an authority, such books and articles have a dogmatic
character. Instead of provisions like "it seems that",
"as we tried to prove" often present in scientific papers,
in popular works there are expressions like "it is a fact
that" or "as science has proven". This has serious
(although not intended) effects on the development of science itself,
for those who are to become scientists in future have their first
contact with a discipline precisely through popular readings. Thus,
what was created by a group of people acquires an impersonal,
autonomous character. "Social distance transforms the author
from a creator to a discoverer"--and this is how a mythical
ideal of knowledge "as representation of reality independent of
the subject of cognition" (1936, VI) arises.



One should then start to read textbooks and experiment under the
supervision of specialists. This introduction into a domain still has
a dogmatic character. An individual's mind is introduced
"into a self-contained world" and acquires a peculiar
mystagogy. Finally, some people become fully-fledged members of a
thought collective of a scientific discipline--specialists:
"the expert is already a specially molded individual who can no
longer escape the bonds of tradition and of the collective; otherwise
he would not be an expert" (1935a, III).



As a specialist she starts to face certain research problems. She does
not face them alone: she is a member of a group, where everybody
perceives the world similarly and thinks about it in (almost) the same
way. And if an issue is new, then any success is achievable only if
the whole group of scholars is engaged. Usually the analyzed phenomena
are extremely complicated and diversified--and they require
distinguishing, segregation, unification, and simplification, and
those are tasks which exceed the capabilities of any single
researcher. "Only through organized cooperative research,
supported by popular knowledge and continuing over several
generations, might a unified picture emerge" (1935a, II.1).



We do not only mean here that there is too much work to do. When
phenomena are not sufficiently examined, we lack concepts by means of
which we could adequately describe them. And we also cannot begin with
gathering facts. Traditionally--and today some still think
so--facts were considered to be what is given and accessible
through the senses. Modern empiricists claimed that there is nothing
in the mind that was not first in the senses. Fleck reversed this
maxim: there is nothing in the senses that was not first in the mind.
So, in order to perceive we have to learn something before. It is not
so that we first see some moving dashes and then we compose a whole of
them. Quite the contrary:



> 
> We walk around without seeing any points, lines, angles, light or
> shadows, from which we would have to arrange "what is
> this" by synthesis or reasoning, but we see at once a house, a
> memorial in a square, a detachment of soldiers, a bookshop window, a
> group of children, a lady with a dog, all of them ready forms.
> (...) We look with our own eyes, but we see with the eyes of the
> collective body, we see the forms whose sense and range of permissible
> transpositions is created by the collective body (1947, II).
> 



This set of forms was transferred to an individual in the process of
socialization. When we bring a layperson to a laboratory and we ask
her to describe a course of scientific experiments, professionals will
find out immediately that she is not able to do this. She will surely
create a long description and bring up a lot of unimportant or
accidental details, but she will not pay attention to what is
important from a scientist's point of view. "If we wanted
necessarily to render his experience in words, the most appropriate
slogan would be: 'I search' or 'I have a
chaos'" (1935b). An expert sees differently than a
layperson because she went through a special training during which she
was familiarized with many examples--e.g. symptoms of a given
disease and at the same time symptoms of other diseases (so with what
*X* is and what *X* is not). At the same time she was
equipped with a certain set of views on what that disease is, on the
course of it, on how it is affected by external conditions etc. Thus,
if the training process is successful a new member of a collective
will directly see the same as what other members see "with their
own eyes". As Fleck states in the last sentence of (1935b),
"'To see' means: to recreate, at a suitable moment,
a picture created by the mental collective to which one
belongs".



However, when a specialist starts research on phenomena of a new kind
she is in the same situation as a layperson: she does not know what
and how to observe. She does not recognize certain forms, she
experiences chaos in which it is very hard to grasp anything constant.
This is why--as it was mentioned above--scholars cannot
start from gathering experimental data. Fleck also stresses that there
is no spontaneous creation of concepts (1935a, II.1). This is why a
new research starts usually--although not always--from
proto-ideas which often are of a religious or philosophical character,
which had existed centuries before they acquired a scientific
character. For example, long before Copernicus there was a proto-idea
of a heliocentric system, before Lavoisier--a proto-idea of
chemical elements, before Dalton--a proto-idea of atom, and
before Leeuwenhoek--a proto-idea of microbe (1935a, II.2).
Proto-ideas are vague, and therefore in the scientific understanding
they cannot be considered as true or false. (Even though they were
true for the members of corresponding thought collectives). But they
can become a point of departure for investigation.



Inquiries cannot be conducted by an isolated researcher, for she would
chase her tail endlessly by repeating old formulas. As we have
mentioned before, the constitution of a research collective is
necessary and it happens when an appropriate mood arises--a mood
which unites people and makes them work. In the case of research that
was analyzed by Fleck, i.e., the research which led to the discovery
of Wassermann's reaction, the source of an appropriate mood was
social pressure--a common demand for effective means for curing
syphilis which was considered as an embarrassing and
reputation-damaging disease. (Fleck brought forward a controversial
claim that the absence of any analogous success in the struggle with
tuberculosis was related to a common approach to tuberculosis as
"romantic", which in turn resulted with insufficient
social pressure to overcome it.) This made the German government join
the process of organizing research teams in that area; an additional
reason was to make achievements of German scientists outmatch
achievements of other nations. "The mood gave a driving power,
and the proto-idea--the direction" (1934).



If a group of people participate in a research program there occurs a
peculiar process. Each member of the group reads different texts (both
popular and professional), participates in different experiments, and
belongs to more or less different thought collectives (both scientific
and non-scientific). So, when they start speaking to each other and
reading each other's papers, a series of misunderstandings
arises. Ideas circulate within a collective and are enriched by new
associations, and therefore the words that are used change their
meanings. Sometimes nothing is left of the original meanings intended
by those participating in the exchange of ideas. Sometimes the changes
stem from a clash of various proto-ideas. And that clash itself is a
result of various social factors. Having conducted countless studies
and conversations and embarked upon a long journey, the scholars
finally create a thought style which nobody intended. And after this
has happened, nobody *post factum* knows when and how that
style started to operate and who, specifically, created it.



> 
> Thoughts pass from one individual to another, each time a little
> transformed, for each individual can attach to them somewhat different
> associations. Strictly speaking, the receiver never understands the
> thought exactly in the way that the transmitter intended it to be
> understood. After a series of such encounters, practically nothing is
> left of the original content. Whose thought is it that continues to
> circulate? It is one that obviously belongs not to any single
> individual but to the collective (1935a, II.4).
> 



Of course this process--an important element of which are
misunderstandings among researchers--cannot be logically
reconstructed.



Together with the mutation of ideas, new forms recognized in
sensations occur. First, when observing phenomena of a new kind one
reaches for the set of known forms--and starts to recognize that
this, what is new, sometimes and under a certain respect resembles
what is known, but some other times and under other respects it is
different. In this period descriptions of results of experiments are
full of comparisons with what one earlier learned to perceive, but
also are full of provisions that those comparisons are sometimes
unreliable. The unreliability manifests itself in the unrepeatability
of initial experiments: something goes differently than before, and we
know neither why it was so, nor what to do in order to get the same
result next time. This raises concerns and the readiness for change. A
researcher acting more or less blindly, searches for some constraints
of thought:



> 
> The work of the research scientist means that in the complex confusion
> and chaos which he faces, he must distinguish that which obeys his
> will from that which arises spontaneously and opposes it. This is the
> firm ground that he, as representative of the thought collective,
> continuously seeks (1935a, IV.2).
> 



Changes in the way of seeing cannot--as it was said
before--be made by an individual. Descriptions of experiments
circulate among scientists, and again as a result of misunderstandings
and understandings the traditional forms are (and this fact is not
noticed by the participants of that process) restyled, some are
rejected, other connected into unique wholes, "and, finally, a
new readiness is formed, i.e. the readiness to see a new, specific
form" (1935b). Finally, in descriptions published in
professional papers comparisons disappear and one states: this and
that was observed. (Similarly, after some time of being in contact
with the Latin alphabet we directly recognize the letter A despite the
enormous variety of shapes it exists in, and at the same time we are
not able to say what this recognizing consists in, cf. Fleck 1947,
I.)



Thus, it is impossible to see something radically new "simply
and immediately": first the constrains of an old thought style
must be removed and a new style must emerge, a collective's
thought mood must change--and this takes time and work with
others. In the course of interpersonal exchange concepts evolve and
facts evolve together with them. This in turn stimulates creation of
new concepts.



> 
> Both thinking and facts are changeable, if only because changes in
> thinking manifest themselves in changed facts. Conversely,
> fundamentally new facts can be discovered only through new thinking
> (1935a, II.4).
> 



Sometimes new ideas come from unexpected directions and without any
relation to science itself. This is how Fleck explains the discovery
of spermatozoon which happened together with the fall of political
absolutism and popularization of the idea of individual freedom
understood mainly as freedom of personal movement. One could not
discover spermatozoon just looking through a microscope. However
someone, who thought about a free person, could notice freely
moving--so "free"--spermatozoa (1939a). This was
the influence of environment which created a restless mood necessary
for searching for something new. And a new mode of thinking created in
a different domain of life allowed one to perceive, distinguish, and
describe it in a way which would stimulate reflections of
others--those participating in revolutionary social changes as
well.



Before new sensual and thought forms arise, a certain "specific
intellectual unrest must arise and a change of the moods of the
thought collective" (1935b). If a person makes an important
discovery but social moods do not change, she will not find people who
take up her ideas and continue research. On the other hand facts are
mutually dependent on each other, so "each new fact
harmoniously--though even so slightly--changes all earlier
facts" (1935a, IV.3). As a result, it sometimes happens that
those initial observations from which a certain research began does
not belong to the same class of facts as the one emerging from that
research. (The research on the variability of bacteria was initiated
by observations made in 1906 by Neisser and Massini, which today are
regarded as bacteriophage effects.) Sometimes nothing remains of the
proto-ideas from which investigations started and which inspired early
experimental work. (Like the proto-idea of syphilis blood has nothing
to do with contemporary Wassermann's reaction). And finally
there arises the edifice of knowledge which was neither intended nor
foreseen by anybody.



In this process there is nothing necessary; various accidental
circumstances decide which ideas become a basis for investigation and
are disseminated within a collective; which meetings between
scientists happen; which research projects acquire social support;
which experiments are conducted first etc. Fleck claims that if e.g.
Sigle's idea of protozoa-like structures as the causative agent
of syphilis had acquired sufficient support, we would have reached a
harmonious system of knowledge different from the current one. The
scope of the name "syphilis" would have been somewhat
different than it is today, just like the methods of research and
therapy would. But when a certain thought style develops and dominates
researchers' minds, alternative ways of development become
closed. Summing up this idea Fleck claims that most--and maybe
even the whole--content of scientific knowledge is conditioned by
historical, psychological and sociological factors and one has to
consider them when attempting to explain that content (1935a,
II.1).



Of course, a series of misunderstandings is not enough to create a
thought style that connects everybody. This is why for the existence
of a certain discipline the main body of an esoteric circle is
necessary--the group composed of general specialists well
prepared to choose among propositions of the vanguard those that are
most useful, and to elaborate, employ and harmonize them with each
other. I.e. to create from a set of provisional claims present in
papers aimed at professionals a system and to pass it on to a next
generation of researchers. This occurs when textbooks are created.



> 
> (...) a judgment about the existence or non-existence of a
> phenomenon belongs, in a democratic collective, to a numerous council,
> not to an individual. The textbook changes the subjective judgment of
> an author into a proven fact. It will be united with the entire system
> of science, it will henceforward be recognized and taught, it will
> become a foundation of further facts and the guiding principle of what
> will be seen and applied (1936, VI).
> 



The social structure of a scientific thought collective is reflected
in types of scientific literature. Papers in scientific journals are
written by scientists working practically on a given problem and are
aimed at other scientists. More general specialists write textbooks
consolidating their esoteric circle and educating its new members.
Popular works are directed to exoteric circles.



The victory of a thought style depends on whether it will be possible
to have a next generation of its followers, and to prevent influences
of other styles. Certain research problems should be propagated, and
other should be removed. A certain mental readiness must be created
among the adepts of science. When it is achieved, all researchers
"will see the new form directly, with their own eyes, as if it
were the only one, everlasting truth, independent of the people"
(1935b). At the end of his life Fleck summarized this as follows:



> 
> Every cognition is a social act (...) for during every lasting
> exchange of thoughts there appear and grow ideas and standards which
> are not associated with any individual author. A communal mode of
> thinking develops which binds all participants, and certainly
> determines every act of cognition. Therefore, cognition must be
> considered as a function of three components: it is a relation between
> the individual subject, the certain object and the given community of
> thinking (*Denkkollektiv*), within which the subject acts; it
> works only when a certain style of thinking (*Denkstil*),
> originating in the given community is used (1986).
> 



The victory of a given thought style is never ultimate. Each new
experimental discovery and every theoretical idea more or less changes
the whole system. Even if at the beginning one sees only what
corresponds with the theory, after a while there appear complications
and exceptions (Kuhn's anomalies) which sooner or later leads to
revisions of concepts and assumptions. "Mutations" in a
thought style, such as contemporary transformations in physics or in
bacteriology, constantly occur. Sooner or later we will have to change
e.g. the law of conservation of energy (1935a, II.1) and any other
concept and claim. In the historical development of science there is
nothing determined once and for all, nothing invariant. Both thinking
and facts change.


## 6. Active and Passive Elements of a Thought Style



Fleck defines a thought style as the readiness for directed
perception, with corresponding mental and objective assimilation of
what has been so perceived, characterized by specific problems of
interest, by judgments which the thought collective considers evident
and by methods which are applied as a means of cognition (1935a,
IV.3). What was collectively developed plays an active role in
cognition: shapes modes of perception and the thinking of members of a
thought collective. An individual, who has assimilated a certain
thought style, becomes passive when conducting standard research:
recognizes in environment specific forms and draws
specific--those and no other--conclusions from an
assimilated theory and results of experimental research.



> 
> Cognition therefore means, primarily, to ascertain those results that
> must follow, given certain preconditions. The preconditions correspond
> to active linkages and constitute that portion of cognition belonging
> to the collective. The constrained results correspond to passive
> linkages and constitute that which is experienced as objective
> reality. The act of ascertaining is the contribution of the individual
> (1935a, II.4).
> 



The occurrence of passive elements cannot be explained sociologically.
They are, so to speak, results of employing a conceptual measure which
resulted from historical and cultural circumstances to the results of
experiments--which, as the title of Fleck's book says, came
to existence together with the creation of a new though style and are
developed with it.



What Fleck calls active elements of a thought style, Henri
Poincare calls "principles" and sees as
"disguised definitions". Poincare stresses that
there is nothing necessary in definitions--they can be various
and they are chosen for pragmatic and aesthetic reasons. Fleck agrees
with him to a certain extent. He notices that in the 19th century
syphilis was defined in many ways: as a carnal scourge, as a
mercury-treated decease, and finally as a set of typical symptoms. And
he claims that "(...) if syphilis can be defined in various
ways, the definition selected still determines some conclusions.
(...) there are some associations which are open to choice
(...) and others that are constrained" (1935a, I). For
example if one defined syphilis as a "carnal scourge",
then other diseases like gonorrhea, soft chancre, etc. would be cases
of syphilis; and when proper experiments had been conducted one stated
for example that "sometimes mercury does not cure the carnal
scourge but makes it even worse". Looking at the same experiment
those who defined syphilis as a disease which can be treated with
mercury would conclude that they are not dealing with syphilis.
However, Fleck opposes the conventionalist idea that definitions can
be chosen freely. Definitions are born with the birth of a thought
style, and their formulation is determined by both historical-cultural
conditioning and by the process of exchanging ideas among researchers
which was described above. A mature thought style is a system where
definitions mutually condition each other and where accepting a
certain definition can prevent accepting some other ones.



The distinction between active and passive elements is still not
clear. Some examples are obvious: if 16 is assumed--on the basis
of some arbitrary convention--as the atomic weight for oxygen,
the atomic weight of hydrogen will necessary be 1.008. "This
means that the ratio of the two weights is a passive element of
knowledge" (1935a, IV.1). However, as an active element of
knowledge Fleck indicates also "the mere use of alcohol in
preparing extracts", adding however that "the actual
usefulness of such extracts is a passive one and therefore a necessary
consequence". He also writes that the concepts of chemical
element and of atom are derived "from collective
imagination", but "the usefulness of these concepts in
chemistry (...) is really independent of the individual
knower". The active and passive elements of knowledge are
inseparable either historically or logically, and every statement can
be divided into active and passive part.



Both kinds of elements can be found in each thought style, and also in
mythical and religious thinking. In one place Fleck notices that
whereas a myth has little passive elements, the characteristic feature
of science is that it attempts to add as many passive elements as it
can to its system. Fleck never developed this idea, and this is
unfortunate, for this could be his contribution to the solution of the
problem of demarcation. There are some places where he makes remarks
complementing argumentation developed in the last chapter: "What
has previously been classed with the passive elements of knowledge may
later join the active ones" (1935a, IV.2). We should regret
again that he did not develop the idea which could contribute to
understanding the mechanism of those transformations which Kuhn later
called "scientific revolutions". For it suggests that not
only pre-scientific proto-ideas, but also passive results obtained
within an old scientific thought style can serve as a starting point
for constructing a new one.


## 7. How a Thought Collective Transforms What Is Socially Constructed Into "Reality"?



As explained above, what and how we see and what and how we think
depends on a collectively created thought style assimilated through
contacts with others. However,



> 
> The individual within the collective is never, or hardly ever,
> conscious of the prevailing thought style, which almost always exerts
> an absolutely compulsive force upon his thinking and with which it is
> not possible to be at variance (1935a, II.4).
> 



It is peculiar that those who participate in social creation of a
thought style do not sometimes realize it either. After years they do
not remember that once they perceived and thought differently, and
they recall their research not as a winding road, full of turns, blind
steps, successes resulting from compensation of accidental errors,
etc. And above all they do not record in their memory those moments
when new ideas appeared as a result of misunderstandings between
researchers. Fleck compares Wassermann's texts from different
periods and his memories on the road which his team took and which
finally led him to the discovery of reaction that now carries his
name. This comparison shows that after years Wassermann did not
realize how in the past, during collective debates and research, facts
and meanings of words, research problems and methods of solving them
had changed. "(...) after fifteen years an identification
between results and intentions had taken place in Wassermann's
thinking. The meandering process of development (...) had become
a straight, goal-directed path" (1935a, III).



Scientists also do not see the changes of facts and concepts that had
happened in their discipline. Since they perceive the world
differently than their predecessors and they think on the basis of
different assumptions, they are not able to understand the meanings of
words from old texts. They do not know that in the past one not so
much thought differently (for incorrectly) about what they now think
about, and perceived differently (for incorrectly) what they perceive,
as one thought of and perceived something else. They instinctively
understand old books and papers according to their own thought style
and consider those texts as steps--although sometimes
erroneous--towards this world-view which they possess now.



The next aspect of social nature of cognition is the phenomenon that
members of a thought collective mutually reinforce themselves in the
conviction that their thought style is true. Members of religious
communities under group pressure do not consider their faith as one of
many, but as the definite truth; they do not consider the principles
of conduct which their faith imposes on them as the principles of one
of many ways of living, but as those grasping of the essence of
morality etc. Also scientists are convinced that their thought style
is at least partially true today, and with time, when they work
together, it will get closer and closer to being true. Yet, one may
say, the conviction as to the truth of a thought style can break down
under the pressure of facts that contradict it, and also as a result
of confrontation with those who think differently. The remarks given
above quite clearly show that this is not the case. Nonetheless let us
summarize Fleck's views on those matters.


1. A thought style is included already in meanings of words, and those
meanings are considered by members of the collective not as something
formed by people but as "objective". Thus, opposing a
system is unthinkable: someone who opposes it is considered to be the
one who does not understand meanings of the words used (1935a, IV.5;
1936, VI).
2. Scientific instruments which embody some results of a thought style,
"direct our thinking automatically on to the tracks of that
style" (1936, VI).
3. Forming our cognitive activity, our perception and thinking,
"[c]ognition modifies the knower so as to adapt him harmoniously
to his acquired knowledge" (1935a, IV.2). Since everybody sees
the world in a way imposed by one's thought style, in every step
one notices facts corresponding with that style and does not notice
what does not fit active assumptions of it.
4. Even if facts incoherent with a given thought style are noticed, one
ignores them as unimportant. For example, for several decades
physicists knew that Mercury had not moved as it should according to
Newton's mechanics, but they failed to mention this fact to the
general public. Only today one precisely describes those facts because
they confirm a new thought style: the general theory of relativity
(1935a, II.3).
5. Cognitive problems we choose to solve do not come from a neutral
reservoir of problems which existed prior to the development of
sciences, but we choose those which are born on the ground of a
thought style imposed on us--and they are usually successfully
solved within its confines. And we do not work with problems which are
born within other styles--our collective considers them not
worthy of attention or even senseless (1935a, IV.3).
6. When anomalies can be no longer ignored, one attempts to show that
they are not incompatible with one's thought style (1935a,
II.3). (Today we would say one adds to the system various *ad
hoc* hypotheses.)
7. Sometimes in old texts we find descriptions of results of experiments
which we, as the users of another thought style, consider illusions.
It happens that somebody sees something what corresponds with
prevailing views and other members of a collective confirm his
experiences (1935a, II.3).



So it is not possible to compare a theory with "reality in
itself". It is true that those who use a thought style give
arguments for their views, but those arguments are of restricted
value. Any attempt to legitimize a particular view is inextricably
bound to standards developed within a given style, and those who
accept those standards accept also the style. So legitimization is
actually unnecessary, for it occurs within a collective with more or
less similar education and a thought-stylized intellectual
constitution. "In science, as in art and in life, only that
which is true to culture is true to nature" (1935a, II.3).



One may however insist, that not only reality exists but also other
people with other thought styles. Can they not convince us that our
thought style is erroneous? No--for every human thinks that those
who belong to the same thought collective as she does are
"normal" and authoritative, and everybody else is
disregarded as more or less "abnormal" (1938). Since
everybody's attention is directed at members of one's
collective, one finds confirmation of one's own views
everywhere. Moreover, the conviction that we have possessed truth is
empowered by the circulation of thoughts between esoteric and exoteric
circles. Laymen accept a specialist's opinion as revelation, and
when that opinion returns from laypersons to the specialist, she
considers it the people's voice confirming her achievements.



When members of various thought collectives meet, a peculiar
phenomenon occurs. One sees passive elements in one's thought
style, but the active ones remain almost unnoticed. However,
"any alien thought style appears like a free flight of fancy,
because he can see only that which is active and almost arbitrary
about it" (1935a, IV.5). Since passive results obtained within
another thought style appear to her as erroneous - as they are
built on an arbitrary and false basis--she is not able to see
their merits and does not understand that people thinking differently
successfully use their own world view. This leads us to the phenomenon
called "incommensurability".


## 8. Incommensurability of Thought Styles and the Problem of Truth



As explained above, when people with different thought styles meet,
they do not fully understand each other, and at the same time one
person thinks that the other is a fool and heretic. Fleck, using
examples from the history of medicine, shows that such a lack of
understanding manifests itself not only where a physicist and a
metaphysician or astrologer meet, but also when today's
scientists read works of their ancestors from the distant past. (Just
like Kuhn Fleck does not think that the history of physics as science
started with Galileo and Newton, and the history of scientific
chemistry with Lavoisier.) For us the views of medieval scholars seem
fantastic, unjustified, useless, so "non-scientific". But
what would happen if they read our "scientific"
dissertations? They would probably consider them artificial,
arbitrary, meaningless. They understood each other well and together
developed their thought styles. Just like our views allow us to deal
with necessities of life, "theological" views allowed our
ancestors to organize life and gave them an understanding of the sense
of life (1935a, IV.5).



On several occasions, especially in (1927) and (1939a), Fleck uses the
term "incommensurability"
(*niewspolmiernosc*) of concepts or
ideas. He does not develop this issue. Yet it is easy--by looking
through the Kuhnian glasses--to extract from his writings a quite
well developed theory of incommensurability of thought styles. Its
core is constituted by the claim that in the historical development of
science there are no invariants.



(a) The language used to describe what to members of a collective
appears as reality changes. Some words disappear, other appear, and
even if words remain their meanings change to a greater or lesser
extent. Fleck quotes some fragments of writings of a physicist James
Clerk Maxwell and a philosopher Henri Bergson on motion and knowledge
on motion and he concludes that the words "motion" and
"knowledge" have different meanings for them: "it is
not as if the word of one of them meant a thing that the other would
give a different name, but that a thing to which one of them gave a
certain name does not exist at all for the other one" (1936,
II). We can find similar examples in writings of
"scientists". Heat in the second half of the 18th century
was on the list of chemical elements, and in the 19th century it
became the motion of atoms. What Lavoisier or Carnot called
"heat", for Maxwell or Boltzmann did not exist and
*vice versa*. So if they could meet and talk they would not
make inconsistent claims about the same phenomenon, but would speak of
something different. "It is not possible to express with
today's words the content of a view of a distant epoch since
particular notions of this epoch are incommensurable with the ones of
today" (1939a).



Obviously, it is not possible to explain to somebody outside of our
thought collective the meanings of the concepts we use through verbal
definitions, for we define words by other words which she does not
understand to the same degree as she does not understand the defined
word. It is not possible to define a word ostensively, for that person
does not perceive in the world those objects which we perceive as
belonging to the scope of the term defined. The only thing we can do
is to teach her the basis of our thought style, like we teach our
children and the young. The first step sometimes consists in creating
a platform of partial understanding with a member of other collective
for the price of impoverishing content and some deformations. But this
is not argumentation but propaganda (1936, III).



(b) After passing from one thought style to another within "the
same" scientific discipline, research problems change. Losses
appear along with benefits. For example, when the contemporary concept
of syphilis was created one learned very much, but many details of
earlier theories were also lost. Earlier researchers did not know many
of the details that we know, but knew more about what according to
them had a greater value. Later researchers see many problems which
their predecessors treated as unimportant or senseless. "This
creates specialized valuation and characteristic intolerance, which
are features shared by all exclusive communities" (1935a, IV.3).
This valuation becomes stronger, for after passing from one thought
style to another the research methods and standards for evaluating
research results change to a greater or lesser extent.



(c) Previous researchers--looking from the same point to the same
direction--did not see what we see, but they saw something we are
not able to see. Those people thought and saw differently than we do
(1935a, IV.5). Their physical reality does not exist for us, and our
physical reality did not exist for them.



This all leads to an extremely anti-realistic standpoint. The thought
style creates reality. Nowadays science is not closer to any objective
picture of the world than the science of 100 years ago (1946). The
only difference is that there are now many more scientists than ever
and as a result our picture of the world is richer in details than any
prior picture. However, the fact that a certain view seems for us to
be true is only a sign of our education and not that of the
correspondence to "an independently existing reality"
(1938). What members of a collective call truth, from the point of
view of sociology of cognition is the up-to-date stage of changes of
thought-style (1936, VI) or stylized thought constraint (1935a,
IV.3).



Since in the historical development of science there is no constant,
unchanging part, since scientific knowledge changes continuously as a
whole, then science does not contain any objective picture of the
world, and it does not even contain any part of such a picture (1946).
Yet contrary to Kuhn, Fleck does not avoid using the term
"truth" in reference to scientific statements. And he
emphasizes that truth is neither subjective nor relative:



> 
> It is always, or almost always, completely determined within a thought
> style. One can never say that the same thought is true for A and false
> for B. If A and B belong to the same thought collective, the thought
> will be either true or false for both. But if they belong to different
> thought collectives, it will just not be the same thought (1935a,
> IV.3).
> 


## 9. Reception



Before World War II there appeared nineteen reviews of Fleck's
book on the genesis and development of a scientific fact, most of them
positive; yet only one was published in a philosophical journal, and
the rest were published in medical or popular journals and newspapers.
After WWII Fleck's epistemology, in spite of all his efforts,
was completely forgotten. Thomas S. Kuhn mentioned his book in the
Preface to *The Structure of Scientific Revolutions* as
"an essay that anticipated many of my own ideas" (Kuhn
1962, p. VII); but for at least fifteen years during fierce debates
provoked by Kuhn's book, nobody paid attention to this remark.
It was only a paper by Wilhelm Baldamus (1977) and a book by his
student Thomas Schnelle (1982) that awakened a broader interest in
Fleck's philosophy and sociology of science. Fleck's book
was republished in the German language in 1980. In 1979 its English
translation *Genesis and Development of a Scientific Fact*
appeared; and between 1986 and 1990 most of Fleck's
epistemological papers became available in English. Fleck's book
and articles was translated into Italian, Polish, Spain, Swedish,
Russian, Ukrainian, Korean, French and Brazilian Portuguese.



Today, in the English speaking world, Fleck is mostly considered to be
an unappreciated forerunner of Thomas Kuhn's theory of
scientific revolutions. It is in the German speaking community of
philosophers and sociologists of science that Fleck is considered to
be a highly original epistemologist, who presents human knowledge in a
quite peculiar and explorative way which significantly transcends
Kuhn's theses. In France there is a group of philosophers and
historians of medicine--Ilana Lowy and others--who
apply Fleck's ideas in their research. In his famous
introduction to the actor-network theory, Bruno Latour named Fleck
"the founder of sociology of science" (Latour 2005, p.
112). In 2005 Ludwik Fleck Zentrum was founded in Collegium
Helveticum, Zurich, led by Johannes Fehr until 2014; since 2015
the centre is managed by Hartmut von Sass. In Brazil Ludwik Fleck has
influenced at least three different "thought collectives":
his theory is applied by historians of science, in teaching and
learning science, and in philosophy (Conde 2016). There is a
group of Serbian archaeologists who are inspired in their work by
Fleck's epistemology (Milosavljevic 2016).