## 1. "Humans", Slogans and the Traditional Package


### 1.1 "Humans"



Before we begin unpacking, it should be noted that the adjective
"human" is polysemous, a fact that often goes unnoticed in
discussions of human nature, but makes a big difference to both the
methodological tractability and truth of claims that employ the
expression. The natural assumption may appear to be that we are
talking about specimens of the biological species *Homo
sapiens*, that is, organisms belonging to the taxon that split
from the rest of the hominin lineage an estimated 150,000 years ago.
However, certain claims seem to be best understood as at least
potentially referring to organisms belonging to various older species
within the subtribe *Homo*, with whom specimens of *Homo
sapiens* share properties that have often been deemed significant
(Sterelny 2018: 114).



On the other hand, the "nature" that is of interest often
appears to be that of organisms belonging to a more restricted group.
There may have been a significant time lag between the speciation of
anatomically modern humans (*Homo sapiens*) and the evolution
of behaviourally modern humans, i.e., human populations whose life
forms involved symbol use, complex tool making, coordinated hunting
and increased geographic range. Behavioural modernity's
development is often believed only to have been completed by 50,000
years ago. If, as is sometimes claimed, behavioural modernity requires
psychological capacities for planning, abstract thought,
innovativeness and symbolism (McBrearty & Brooks 2000: 492) and if
these were not yet widely or sufficiently present for several tens of
thousands of years after speciation, then it may well be
behaviourally, rather than anatomically modern humans whose
"nature" is of interest to many theories. Perhaps the
restriction might be drawn even tighter to include only contemporary
humans, that is, those specimens of the species who, since the
introduction of agriculture around 12,000 years ago, evolved the
skills and capacities necessary for life in large sedentary,
impersonal and hierarchical groups (Kappeler, Fichtel, & van
Schaik 2019: 68).



It was, after all, a Greek living less than two and a half millennia
ago within such a sedentary, hierarchically organised population
structure, who could have had no conception of the prehistory of the
beings he called *anthropoi*, whose thoughts on their
"nature" have been decisive for the history of
philosophical reflection on the subject. It seems highly likely that,
without the influence of Aristotle, discussions of "human
nature" would not be structured as they are until today.


### 1.2 Unpacking the Traditional Package



We can usefully distinguish four types of claim that have been
traditionally made using the expression "human nature". As
a result of a particular feature of Aristotle's philosophy, to
which we will come in a moment, these four claims are associated with
five different uses of the expression. Uses of the first type seem to
have their origin in Plato; uses of the second, third and fourth type
are Aristotelian; and, although uses of the fifth type have
historically been associated with Aristotle, this association seems to
derive from a misreading in the context of the religiously motivated
Mediaeval reception of his philosophy.



A *first*, thin, contrastive use of the expression "human
nature" is provided by the application of a thin, generic
concept of nature to humans. In this minimal variant, nature is
understood in purely contrastive or negative terms. *Phusis* is
contrasted in Plato and Aristotle with *techne*, where the
latter is the product of intention and a corresponding intervention of
agency. If the entire cosmos is taken to be the product of divine
agency, then, as Plato argued (Nadaf 2005: 1ff.), conceptualisations
of the cosmos as natural in this sense are mistaken. Absent divine
agency, the types of agents whose intentions are relevant for the
status of anything as natural are human agents. Applied to humans,
then, this concept of nature picks out human features that are not the
results of human intentional action. Thus understood, human nature is
the set of human features or processes that remain after subtraction
of those picked out by concepts of the non-natural, concepts such as
"culture", "nurture", or
"socialisation".



A *second* component in the package supplies the thin concept
with substantial content that confers on it explanatory power.
According to Aristotle, natural entities are those that contain in
themselves the principle of their own production or development, in
the way that acorns contain a blueprint for their own realisation as
oak trees (*Physics* 192b; *Metaphysics* 1014b). The
"nature" of natural entities thus conceptualised is a
subset of the features that make up their nature in the first sense.
The human specification of this explanatory concept of nature aims to
pick out human features that similarly function as blueprints for
something like a fully realised form. According to Aristotle, for all
animals that blueprint is "the soul", that is, the
integrated functional capacities that characterise the fully developed
entity. The blueprint is realised when matter, i.e., the body, has
attained the level of organisation required to instantiate the
animal's living functions (Charles 2000: 320ff.; Lennox 2009:
356).



A terminological complication is introduced here by the fact that the
fully developed form of an entity is itself also frequently designated
as its "nature" (Aristotle, *Physics* 193b;
*Politics* 1252b). In Aristotle's teleological
metaphysics, this is the entity's end, "that for the sake
of which a thing is" (*Metaphysics* 1050a; Charles 2000:
259). Thus, a human's "nature", like that of any
other being, may be either the features in virtue of which it is
disposed to develop to a certain mature form or, *thirdly*, the
form to which it is disposed to develop.



Importantly, the particularly prominent focus on the idea of a fully
developed form in Aristotle's discussions of humans derives from
its dual role. It is not only the form to the realisation of which
human neonates are disposed; it is also the form that mature members
of the species *ought to* realise (*Politics* 1253a).
This normative specification is the *fourth* component of the
traditional package. The second, third and fourth uses of
"nature" are all in the original package firmly anchored
in a teleological metaphysics. One question for systematic claims
about human nature is whether any of these components remain plausible
if we reject a teleology firmly anchored in theology (Sedley 2010:
5ff.).



A *fifth and last* component of the package that has
traditionally been taken to have been handed down from antiquity is
classificatory. Here, the property or set of properties named by the
expression "human nature" is that property or property set
in virtue of the possession of which particular organisms belong to a
particular biological taxon: what we now identify as the species taxon
*Homo sapiens*. This is human nature typologically
understood.



This, then, is the traditional package:




|  |  |
| --- | --- |
| *Component* | *Variant of human nature* |
| TP1 | contrastive |
| TP2 | blueprint explanatory |
| TP3 | explanatorily teleological |
| TP4 | normatively teleological |
| TP5 | classificatory or taxonomic |


### 1.3 Essentialisms



The sort of properties that have traditionally been taken to support
the classificatory practices relevant to TP5 are intrinsic to the
individual organisms in question. Moreover, they have been taken to be
able to fulfil this role in virtue of being *necessary and
sufficient* for the organism's membership of the species,
i.e., "essential" in one meaning of the term. This view of
species membership, and the associated view of species themselves, has
been influentially dubbed "typological thinking" (Mayr
1959 [1976: 27f.]; cf. Mayr 1982: 260) and "essentialism"
(Hull 1965: 314ff.; cf. Mayr 1968 [1976: 428f.]). The former
characterisation involves an epistemological focus on the
classificatory procedure, the latter a metaphysical focus on the
properties thus singled out. Ernst Mayr claimed that the
classificatory approach originates in Plato's theory of forms,
and, as a result, involves the further assumption that the properties
are unchanging. According to David Hull, its root cause is the attempt
to fit the ontology of species taxa to an Aristotelian theory of
definition.



The theory of definition developed in Aristotle's logical works
assigns entities to a genus and distinguishes them from other members
of the genus, i.e., from other "species", by their
differentiae (*Topics* 103b). The procedure is descended from
the "method of division" of Plato, who provides a crude
example as applied to humans, when he has the Eleatic Stranger in the
*Statesman* characterise them as featherless bipeds (266e).
Hull and many scholars in his wake (Dupre 2001: 102f.) have
claimed that this simple schema for picking out essential conditions
for species membership had a seriously deleterious effect on
biological taxonomy until Darwin (cf. Winsor 2006).



However, there is now widespread agreement that Aristotle was no
taxonomic essentialist (Balme 1980: 5ff.; Mayr 1982: 150ff.; Balme
1987: 72ff.; Ereshefsky 2001: 20f; Richards 2010: 21ff.; Wilkins 2018:
9ff.). First, the distinction between genus and differentiae was for
Aristotle relative to the task at hand, so that a
"species" picked out in this manner could then count as
the genus for further differentiation. Second, the Latin term
"species", a translation of the Greek *eidos*, was
a logical category with no privileged relationship to biological
entities; a prime example in the *Topics* is the species
justice, distinguished within the genus virtue (143a). Third, in a key
methodological passage, *Parts of Animals*, I.2-3
(642b-644b), Aristotle explicitly rejects the method of
"dichotomous division", which assigns entities to a genus
and then seeks a single differentia, as inappropriate to the
individuation of animal kinds. Instead, he claims, a multiplicity of
differentiae should be brought to bear. He emphasises this point in
relation to humans (644a).



According to Pierre Pellegrin and David Balme, Aristotle did not seek
to establish a taxonomic system in his biological works (Pellegrin
1982 [1986: 113ff.]; Balme 1987, 72). Rather, he simply accepted the
everyday common sense partitioning of the animal world (Pellegrin 1982
[1986: 120]; Richards 2010: 24; but cf. Charles 2000: 343ff.). If this
is correct, Aristotle didn't even ask after the conditions for
belonging to the species *Homo sapiens*. So he wasn't
proposing any particular answer, and specifically not the
"essentialist" answer advanced by TP5. In as far as such
an answer has been employed in biological taxonomy (cf. Winsor 2003),
its roots appear to lie in Neoplatonic, Catholic misinterpretations of
Aristotle (Richards 2010: 34ff.; Wilkins 2018: 22ff.). Be that as it
may, the fifth use of "human nature" transported by
tradition--to pick out essential conditions for an
organism's belonging to the species--is of eminent
interest. The systematic concern behind Mayr and Hull's
historical claims is that accounts of the form of TP5 are incompatible
with evolutionary theory. We shall look at this concern in
 section 2
 of this entry.



Because the term "essentialism" recurs with different
meanings in discussions of human nature and because some of the
theoretical claims thus summarised are assumed to be Aristotelian in
origin, it is worth spending a moment here to register what claims can
be singled out by the expression. The *first*, purely
classificatory conception just discussed should be distinguished from
a *second* view that is also frequently labelled
"essentialist" and which goes back to Locke's
concept of "real essence" (1689: III, iii, 15). According
to essentialism thus understood, an essence is the intrinsic feature
or features of an entity that fulfils or fulfil a dual role: firstly,
of being that in virtue of which something belongs to a kind and,
secondly, of explaining why things of that kind typically have a
particular set of observable features. Thus conceived,
"essence" has both a classificatory and an explanatory
function and is the core of a highly influential,
"essentialist" theory of natural kinds, developed in the
wake of Kripke's and Putnam's theories of reference.



An account of human nature that is essentialist in this sense would
take the nature of the human natural kind to be a set of
microstructural properties that have two roles: first, they constitute
an organism's membership of the species *Homo sapiens*.
Second, they are causally responsible for the organism manifesting
morphological and behavioural properties typical of species members.
Paradigms of entities with such natures or essences are chemical
elements. An example is the element with the atomic number 79, the
microstructural feature that accounts for surface properties of gold
such as yellowness. Applied to organisms, it seems that the relevant
explanatory relationship will be developmental, the microstructures
providing something like a blueprint for the properties of the mature
individual. Kripke assumed that some such blueprint is the
"internal structure" responsible for the typical
development of tigers as striped, carnivorous quadrupeds (Kripke 1972
[1980: 120f.]).



As the first, pseudo-Aristotelian version of essentialism illustrates,
the classificatory and explanatory components of what we might call
"Kripkean essentialism" can be taken apart. Thus,
"human nature" can also be understood in exclusively
explanatory terms, viz. as the set of microstructural properties
responsible for typical human morphological and behavioural features.
In such an account, the ability to pick out the relevant organisms is
simply presupposed. As we shall see in
 section 4
 of this entry, accounts of this kind have been popular in the
contemporary debate. The subtraction of the classificatory function of
the properties in these conceptions has generally seemed to warrant
withholding from them the label "essentialist". However,
because some authors have still seen the term as applicable
(Dupre 2001: 162), we might think of such accounts as
constituting a *third*, weak or deflationary variant of
essentialism.



Such purely explanatory accounts are descendants of the second use of
"human nature" in the traditional package, the difference
being that they don't usually presuppose some notion of the
fully developed human form. However, where some such presupposition is
made, there are stronger grounds for talking of an
"essentialist" account. Elliott Sober has argued that the
key to essentialism is not classification in terms of necessary and
sufficient conditions, but the postulation of some "privileged
state", to the realisation of which specimens of a species tend,
as long as no extrinsic factors "interfere" (Sober 1980:
358ff.). Such a dispositional-teleological conception, dissociated
from classificatory ambitions, would be a *fourth* form of
essentialism. Sober rightly associates such an account with Aristotle,
citing Aristotle's claims in his zoological writings that
interfering forces are responsible for deviations, i.e., morphological
differences, both within and between species. A contemporary account
of human nature with this structure will be discussed in
 section 4.



A *fifth* and final form of essentialism is even more clearly
Aristotelian. Here, an explicitly normative status is conferred on the
set of properties to the development of which human organisms tend.
For normative essentialism, "the human essence" or
"human nature" is a normative standard for the evaluation
of organisms belonging to the species. Where the first, third and
fourth uses of the expression have tended to be made with critical
intent (for defensive exceptions, see Charles 2000: 348ff.; Walsh
2006; Devitt 2008; Boulter 2012), this fifth use is more often a
self-ascription (e.g., Nussbaum 1992). It is intended to emphasise
metaethical claims of a specific type. According to such claims, an
organism's belonging to the human species entails or in some way
involves the applicability to the organism of moral norms that ground
in the value of the fully developed human form. According to one
version of this thought, humans ought be, or ought to be enabled to
be, rational because rationality is a key feature of the fully
developed human form. Such normative-teleological accounts of human
nature will be the focus of
 section 5.2.



We can summarise the variants of essentialism and their relationship
to the components of the traditional package as follows:




|  |  |
| --- | --- |
| Type of essentialism | Relationship to the traditional package |
| purely classificatory | equivalent to TP5 |
| purely explanatory | unspecific version of TP2 |
| explanatory-classificatory | combines TP5 with an unspecific version of TP2 |
| explanatorily teleological | equivalent to TP3 |
| normatively teleological | equivalent to TP4 |



Section 2
 and
 section 5
 of this entry deal with the purely classificatory and the normative
teleological conceptions of human nature respectively, and with the
associated types of essentialism.
 Section 3
 discusses attempts to downgrade TP5, moving from essential to merely
characteristic properties.
 Section 4
 focuses on accounts of an explanatory human nature, both on attempts
to provide a modernized version of the teleological blueprint model
 (SS4.1)
 and on explanatory conceptions with deflationary intent relative to
the claims of TP2 and TP3
 (SS4.2
 and
 SS4.3).


### 1.4 On the Status of *the* Traditional Slogan



The traditional package specifies a set of conditions some or all of
which substantial claims about "human nature" are supposed
to meet. Before we turn to the systematic arguments central to
contemporary debates on whether such conditions can be met, it will be
helpful to spend a moment considering one highly influential
substantial claim. Aristotle's writings prominently contain two
such claims that have been handed down in slogan form. The first is
that the human being (more accurately: "man") is an animal
that is in some important sense social ("zoon politikon",
*History of Animals* 487b; *Politics* 1253a;
*Nicomachean Ethics* 1169b). According to the second,
"he" is a rational animal (*Politics* 1253a, where
Aristotle doesn't actually use the traditionally ascribed
slogan, "zoon logon echon").



Aristotle makes both claims in very different theoretical contexts, on
the one hand, in his zoological writings and, on the other, in his
ethical and political works. This fact, together with the fact that
Aristotle's philosophy of nature and his practical philosophy
are united by a teleological metaphysics, may make it appear obvious
that the slogans are biological claims that provide a foundation for
normative claims in ethics and politics. The slogans do indeed
function as foundations in the *Politics* and the
*Nicomachean Ethics* respectively (on the latter, see
 section 5
 of this entry). It is, however, unclear whether they are to be
understood as biological claims. Let us focus on the slogan that has
traditionally dominated discussions of human nature in Western
philosophy, that humans are "rational animals".



First, if Pellegrin and Balme are right that Aristotelian zoology is
uninterested in classifying species, then ascribing the capacity for
"rationality" cannot have the function of naming a
biological trait that distinguishes humans from other animals. This is
supported by two further sets of considerations. To begin with,
Aristotle's explicit assertion that a series of
*differentiae* would be needed to "define" humans
(*Parts of Animals* 644a) is cashed out in the long list of
features he takes to be their distinguishing marks, such as speech,
having hair on both eyelids, blinking, having hands, upright posture,
breasts in front, the largest and moistest brain, fleshy legs and
buttocks (Lloyd 1983: 29ff.). Furthermore, there is in Aristotle no
capacity for reason that is both exclusive to, and universal among
*anthropoi*. One part or kind of reason, "practical
intelligence" (*phronesis*), is, Aristotle claims, found
in both humans and other animals, being merely superior in the former
(*Parts of Animals*, 687a). Now, there are other forms of
reasoning of which this is not true, forms whose presence are
sufficient for being human: humans are the only animals capable of
deliberation (*History of Animals* 488b) and reasoning (*to
noein*), in as far as this extends to mathematics and first
philosophy. Nevertheless, these forms of reasoning are unnecessary:
slaves, who Aristotle includes among humans (*Politics* 1255a),
are said to have no deliberative faculty (*to bouleutikon*) at
all (*Politics* 1260a; cf. Richter 2011: 42ff.). Presumably,
they will also be without the capacities necessary for first
philosophy.



Second, these Aristotelian claims raise the question as to whether the
ascription of rationality is even intended as an ascription to an
individual in as far as she or he belongs to a biological kind. The
answer might appear to be obviously affirmative. Aristotle uses the
claim that a higher level of reason is characteristic of humans to
teleologically explain other morphological features, in particular
upright gait and the morphology of the hands (*Parts of
Animals* 686a, 687a). However, the kind of reason at issue here is
practical intelligence, the kind humans and animals share, not the
capacity for mathematics and metaphysics, which among animals is
exercised exclusively by humans. In as far as humans are able to
exercise this latter capacity in contemplation, Aristotle claims that
they "partake of the divine" (*Parts of Animals*
656a), a claim of which he makes extensive use when grounding his
ethics in human rationality (*Nicomachean Ethics*
1177b-1178b). When, in a passage to which James Lennox has drawn
attention (Lennox 1999), Aristotle declares that the rational part of
the soul cannot be the object of natural science (*Parts of
Animals* 645a), it seems to be the contemplative part of the soul
that is thus excluded from biological investigation, precisely the
feature that is named in the influential slogan. If it is the
"something divine ... present in" humans that is
decisively distinctive of their kind, it seems unclear whether the
relevant kind is biological.



It is not the aim of this entry to decide questions of Aristotle
interpretation. What is important is that the relationship of the
question of "human nature" to biology is, from the
beginning of the concept's career, not as unequivocal as is
often assumed (e.g., Hull 1986: 7; Richards 2010: 217f.). This is
particularly true of the slogan according to which humans are rational
animals. In the history of philosophy, this slogan has frequently been
detached from any attempt to provide criteria for biological
classification or characterisation. When Aquinas picks up the slogan,
he is concerned to emphasise that human nature involves a material,
corporeal aspect. This aspect is, however, not thought of in
biological terms. Humans are decisively "rational
substances", i.e., persons. As such they also belong to a kind
whose members also number angels and God (three times) (Eberl 2004).
Similarly, Kant is primarily, indeed almost exclusively, interested in
human beings as examples of "rational nature",
"human nature" being only one way in which rational nature
can be instantiated (Kant 1785, 64, 76, 85). For this reason, Kant
generally talks of "rational beings", rather than of
"rational animals" (1785, 45, 95).



There is, then, a perspective on humans that is plausibly present in
Aristotle, stronger in Aquinas and dominant in Kant and that involves
seeing them as instances of a kind other than the "human
kind", i.e., seeing the human animal "as a rational
being" (Kant 1785 [1996: 45]). According to this view, the
"nature" of humans that is most worthy of philosophical
interest is the one they possess not insofar as they are human, but
insofar as they are rational. Where this is the relevant use of the
concept of human nature, being a specimen of the biological species is
unnecessary for possessing the corresponding property. Specimens of
other species, as well as non-biological entities may also belong to
the relevant kind. It is also insufficient, as not all humans will
have the properties necessary for membership in that kind.



As both a biologist and ethicist, Aristotle is at once a detached
scientist and a participant in forms of interpersonal and political
interaction only available to contemporary humans living in large,
sedentary subpopulations. It seems plausible that a participant
perspective may have suggested a different take on what it is to be
human, perhaps even a different take on the sense in which humans
might be rational animals, to that of biological science. We will
return to this difference in
 section 5
 of the entry.


## 2. The Nature of the Evolutionary Unit *Homo sapiens* and its Specimens



Detailing the features in virtue of which an organism is a specimen of
the species *Homo sapiens* is a purely biological task. Whether
such specification is achievable and, if so how, is controversial. It
is controversial for the same reasons for which it is controversial
what conditions need to be met for an organism to be a specimen of any
species. These reasons derive from the theory of evolution.



A first step to understanding these reasons involves noting a further
ambiguity in the use of the expression "human nature",
this time an ambiguity specific to taxonomy. The term can be used to
pick out a set of properties as an answer to two different questions.
The first concerns the properties of some *organism* which make
it the case that it *belongs to* the species *Homo
sapiens*. The second concerns the properties in virtue of which a
*population or metapopulation is* the species *Homo
sapiens*. Correspondingly, "human nature" can pick out
either the properties of organisms that constitute their partaking in
the species *Homo sapiens* or the properties of some
higher-level entity that constitute it as that species. Human nature
might then either be the nature of the species or the nature of
species specimens as specimens of the species.



It is evolution that confers on this distinction its particular form
and importance. The variation among organismic traits, without which
there would be no evolution, has its decisive effects at the level of
populations. These are groups of organisms that in some way cohere at
a time in spite of the variation of traits among the component
organisms. It is population-level groupings, taxa, not organisms, that
evolve and it is taxa, such as species, that provide the organisms
that belong to them with genetic resources (Ghiselin 1987: 141). The
species *Homo sapiens* appears to be a metapopulation that
coheres at least in part because of the gene flow between its
component organisms brought about by interbreeding (cf. Ereshefsky
1991: 96ff.). Hence, according to evolutionary theory, *Homo
sapiens* is plausibly a higher-level entity--a unit of
evolution--consisting of the lower-level entities that are
individual human beings. The two questions phrased in terms of
"human nature" thus concern the conditions for
individuation of the population-level entity and the conditions under
which organisms are components of that entity.


### 2.1 The Nature of the Species Taxon



The theory of evolution transforms the way we should understand the
relationship between human organisms and the species to which they
belong. The taxonomic assumption of TP5 was that species are
individuated by means of intrinsic properties that are individually
instantiated by certain organisms. Instantiating those properties is
taken to be necessary and sufficient for those organisms to belong to
the species. Evolutionary theory makes it clear that species, as
population-level entities, cannot be individuated by means of the
properties of lower-level constituents, in our case, of individual
human organisms (Sober 1980: 355).



The exclusion of this possibility grounds a decisive difference from
the way natural kinds are standardly construed in the wake of Locke
and Kripke. Recall that, in this Kripkean construal, lumps of matter
are instances of chemical kinds because of their satisfaction of
intrinsic necessary and sufficient conditions, viz. their atoms
possessing a certain number of protons. The same conditions also
individuate the chemical kinds themselves. Chemical kinds are thus
spatiotemporally unrestricted sets. This means that there are no
metaphysical barriers to the chance generation of members of the kind,
independently of whether the kind is instantiated at any contiguous
time or place. Nitrogen could come to exist by metaphysical
happenstance, should an element with the atomic number 14 somehow come
into being, even in a world in which up to that point no nitrogen has
existed (Hull 1978: 349; 1984: 22).



In contrast, a species can only exist at time \(t\_n\) if either it or
a parent species existed at \(t\_{n-1}\) and there was some
relationship of spatial contiguity between component individuals of
the species at \(t\_n\) and the individuals belonging to either the
same species or the parent species at \(t\_{n-1}\). This is because of
the essential role of the causal relationship of heredity. Heredity
generates both the coherence across a population requisite for the
existence of a species and the variability of predominant traits
within the population, without which a species would not evolve.



For this reason, the species *Homo sapiens*, like every other
species taxon, must meet a historical or genealogical condition. (For
pluralistic objections to even this condition, see Kitcher 1984:
320ff.; Dupre 1993: 49f.) This condition is best expressed as a
segment of a population-level phylogenetic tree, where such trees
represent ancestor-descendent series (Hull 1978: 349; de Queiroz 1999:
50ff.; 2005). Species, as the point is often put, are historical
entities, rather than kinds or classes (Hull 1978: 338ff.; 1984: 19).
The fact that species are not only temporally, but also spatially
restricted has also led to the stronger claim that they are
individuals (Ghiselin 1974; 1997: 14ff.; Hull 1978: 338). If this is
correct, then organisms are not members, but *parts* of species
taxa. Independently of whether this claim is true for all biological
species, *Homo sapiens* is a good candidate for a species that
belongs to the category *individual*. This is because the
species is characterised not only by spatiotemporal continuity, but
also by causal processes that account for the coherence between its
component parts. These processes plausibly include not only
interbreeding, but also conspecific recognition and particular forms
of communication (Richards 2010: 158ff., 218).



Importantly, the genealogical condition is only a necessary condition,
as genealogy unites all the segments of one lineage. The segment of
the phylogenetic tree that represents some species taxon begins with a
node that represents a lineage-splitting or speciation event.
Determining that node requires attention to general speciation theory,
which has proposed various competing criteria (Dupre 1993:
48f.; Okasha 2002: 201; Coyne & Orr 2004). In the case of *Homo
sapiens*, it requires attention to the specifics of the human
case, which are also controversial (see Crow 2003; Cela-Conde &
Ayala 2017: 11ff.). The end point of the segment is marked either by
some further speciation event or, as may seem likely in the case of
*Homo sapiens*, by the destruction of the metapopulation. Only
when the temporal boundaries of the segment have become determinate
would it be possible to adduce sufficient conditions for the existence
of such a historical entity. Hence, if "human nature" is
understood to pick out the necessary and sufficient conditions that
individuate the species taxon *Homo sapiens*, its content is
not only controversial, but epistemically unavailable to us.


### 2.2 The Nature of Species Specimens as Species Specimens



If we take such a view of the individuating conditions for the species
*Homo sapiens*, what are the consequences for the question of
which organisms belong to the species? It might appear that it leaves
open the possibility that speciation has resulted in some intrinsic
property or set of properties establishing the cohesion specific to
the taxon and that such properties count as necessary and sufficient
for belonging to it (cf. Devitt 2008: 17ff.). This appearance would be
deceptive. To begin with, no intrinsic property can be necessary
because of the sheer empirical improbability that all species
specimens grouped together by the relevant lineage segment instantiate
any such candidate property. For example, there are individuals who
are missing legs, inner organs or the capacity for language, but who
remain biologically human (Hull 1986: 5). Evolutionary theory
clarifies why this is so: variability, secured by mechanisms such as
mutation and recombination, is the key to evolution, so that, should
some qualitative property happen to be universal among all extant
species specimens immediately after the completion of speciation, that
is no guarantee that it will continue to be so throughout the lifespan
of the taxon (Hull 1984: 35; Ereshefsky 2008: 101). The common thought
that there must be at least some genetic property common to all human
organisms is also false (R. Wilson 1999a: 190; Sterelny &
Griffiths 1999: 7; Okasha 2002: 196f.): phenotypical properties that
are shared in a population are frequently co-instantiated as a result
of the complex interaction of differing gene-regulatory networks.
Conversely, the same network can under different circumstances lead to
differing phenotypical consequences (Walsh 2006: 437ff.). Even if it
should turn out that every human organism instantiated some property,
this would be a contingent, rather than a necessary fact (Sober 1980:
354; Hull 1986: 3).



Moreover, the chances of any such universal property also being
sufficient are vanishingly small, as the sharing of properties by
specimens of other species can result from various mechanisms, in
particular from the inheritance of common genes in related species and
from parallel evolution. This doesn't entail that there may be
no intrinsic properties that are sufficient belonging to the species.
There are fairly good candidates for such properties, if we compare
humans with other terrestrial organisms. Language use and a
self-understanding as moral agents come to mind. However, whether
non-terrestrial entities might possess such properties is an open
question. And decisively, they are obviously hopeless as necessary
conditions (cf. Samuels 2012: 9).



This leaves only the possibility that the conditions for belonging to
the species are, like the individuating conditions for the species
taxon, relational. Lineage-based individuation of a taxon depends on
its component organisms being spatially and temporally situated in
such a way that the causal processes necessary for the inheritance of
traits can take place. In the human case, the key processes are those
of sexual reproduction. Therefore, being an organism that belongs to
the species *Homo sapiens* is a matter of being connected
reproductively to organisms situated unequivocally on the relevant
lineage segment. In other words, the key necessary condition is having
been sexually reproduced by specimens of the species (Kronfeldner
2018: 100). Hull suggests that the causal condition may be
disjunctive, as it could also be fulfilled by a synthetic entity
created by scientists that produces offspring with humans who have
been generated in the standard manner (Hull 1978: 349). Provided that
the species is not in the throes of speciation, such direct descent or
integration into the reproductive community, i.e., participation in
the "complex network [...] of mating and
reproduction" (Hull 1986: 4), will also be sufficient.


### 2.3 Responding to the Evolutionary Verdict on Classificatory Essences



The lack of a "human essence" in the sense of intrinsic
necessary and sufficient conditions for belonging to the species taxon
*Homo sapiens*, has led a number of philosophers to deny that
there is any such thing as human nature (Hull 1984: 19; 1986; Ghiselin
1997: 1; de Sousa 2000). As this negative claim concerns properties
intrinsic both to relevant organisms and to the taxon, it is equally
directed at the "nature" of the organisms as species
specimens and at that of the species taxon itself. An alternative
consists in retracting the condition that a classificatory essence
must be intrinsic, a move which allows talk of a historical or
relational essence and a corresponding relational conception of
taxonomic human nature (Okasha 2002: 202).



Which of these ways of responding to the challenge from evolutionary
theory appears best is likely to depend on how one takes it that the
classificatory issues relate to the other matters at stake in the
original human nature package. These concern the explanatory and
normative questions raised by TP1-TP4. We turn to these in the
following three sections of this article.



An exclusively genealogical conception of human nature is clearly not
well placed to fulfil an explanatory role comparable to that envisaged
in the traditional package. What might have an explanatory function
are the properties of the entities from which the taxon or its
specimens are descended. Human nature, genealogically understood,
might serve as the conduit for explanations in terms of such
properties, but will not itself explain anything. After all,
integration in a network of sexual reproduction will be partly
definitive of the specimens of all sexual species, whilst what is to
be explained will vary enormously across taxa.



This lack of fit between classificatory and explanatory roles
confronts us with a number of further theoretical possibilities. For
example, one might see this incompatibility as strengthening the
worries of eliminativists such as Ghiselin and Hull: even if the
subtraction of intrinsicality were not on its own sufficient to
justify abandoning talk of human nature, its conjunction with a lack
of explanatory power, one might think, certainly is (Dupre
2003: 109f.; Lewens 2012: 473). Or one might argue that it is the
classificatory ambitions associated with talk of human nature that
should be abandoned. Once this is done, one might hope that certain
sets of intrinsic properties can be distinguished that figure
decisively in explanations and that can still justifiably be labelled
"human nature" (Roughley 2011: 15; Godfrey-Smith 2014:
140).



Taking this second line in turn raises two questions: first, in what
sense are the properties thus picked out specifically
"human", if they are neither universal among, nor unique
to species specimens? Second, in what sense are the properties
"natural"? Naturalness as independence from the effects of
human intentional action is a key feature of the original package
(TP1). Whether some such conception can be coherently applied to
humans is a challenge for any non-classificatory account.


## 3. Characteristic Human Properties


### 3.1 Privileging Properties



The answer given by TP2 to the first question was in terms of the
fully developed human form, where "form" does not refer
solely to observable physical or behavioural characteristics, but also
includes psychological features. This answer entails two claims:
first, that there is one single such "form", i.e.,
property or set of properties, that figures in explanations that range
across individual human organisms. It also entails that there is a
point in human development that counts as "full", that is,
as development's goal or "telos". These claims go
hand in hand with the assumption that there is a distinction to be
drawn between normal and abnormal adult specimens of the species.
There is, common sense tells us, a sense in which normal adult humans
have two legs, two eyes, one heart and two kidneys at specific
locations in the body; they also have various dispositions, for
instance, to feel pain and to feel emotions, and a set of capacities,
such as for perception and for reasoning. And these, so it seems, may
be missing, or under- or overdeveloped in abnormal specimens.



Sober has influentially described accounts that work with such
teleological assumptions as adhering to an Aristotelian "Natural
State Model" (Sober 1980: 353ff.). Such accounts work with a
distinction that has no place in evolutionary biology, according to
which variation of properties across populations is the key to
evolution. Hence, no particular end states of organisms are privileged
as "natural" or "normal" (Hull 1986: 7ff.). So
any account that privileges particular morphological, behavioural or
psychological human features has to provide good reasons that are both
non-evolutionary and yet compatible with the evolutionary account of
species. Because of the way that the notion of the normal is
frequently employed to exclude and oppress, those reasons should be
particularly good (Silvers 1998; Dupre 2003: 119ff.; Richter
2011: 43ff.; Kronfeldner 2018: 15ff.).



The kinds of reasons that may be advanced could either be internal to,
or independent of the biological sciences. If the former, then various
theoretical options may seem viable. The *first* grounds in the
claim that, although species are not natural kinds and are thus
unsuited to figuring in laws of nature (Hull 1987: 171), they do
support descriptions with a significant degree of generality, some of
which may be important (Hull 1984: 19). A theory of human nature
developed on this basis should explain the kind of importance on the
basis of which particular properties are emphasised. The
*second* theoretical option is pluralism about the metaphysics
of species: in spite of the fairly broad consensus that species are
defined as units of evolution, the pluralist can deny the primacy of
evolutionary dynamics, arguing that other epistemic aims allow the
ecologist, the systematist or the ethologist to work with an equally
legitimate concept of species that is not, or not exclusively
genealogical (cf. Hull 1984: 36; Kitcher 1986: 320ff.; Hull 1987:
178-81; Dupre 1993: 43f.). The *third* option
involves a relaxation of the concept of natural kinds, such that it no
longer entails the instantiation of intrinsic, necessary, sufficient
and spatiotemporally unrestricted properties, but is nevertheless able
to support causal explanations. Such accounts aim to reunite taxonomic
and explanatory criteria, thus allowing species taxa to count as
natural kinds after all (Boyd 1999a; R. Wilson, Barker, & Brigandt
2007: 196ff.). Where, *finally*, the reasons advanced for
privileging certain properties are independent of biology, these tend
to concern features of
humans'--"our"--self-understanding as
participants in, rather than observers of, a particular form of life.
These are likely to be connected to normative considerations. Here
again, it seems that a special explanation will be required for why
these privileged properties should be grouped under the rubric
"human nature".



The accounts to be described in the next
 subsection (3.2)
 of this entry are examples of the first strategy.
 Section 4
 includes discussion of the relaxed natural kinds strategy.
 Section 5
 focuses on accounts of human nature developed from a participant
perspective and also notes the support that the pluralist metaphysical
strategy might be taken to provide.


### 3.2 Statistical Normality or Robust Causality



Begin, then, with the idea that to provide an account of "human
nature" is to circumscribe a set of generalisations concerning
humans. An approach of this sort sees the properties thus itemised as
specifically "human" in as far as they are common among
species specimens. So the privilege accorded to these properties is
purely statistical and "normal" means statistically
normal. Note that taking the set of statistically normal properties of
humans as a non-teleological replacement for the fully developed human
form retains from the original package the possibility of labelling as
"human nature" either those properties themselves (TP3) or
their developmental cause (TP2). Either approach avoids the
classificatory worries dealt with in
 section 2:
 it presupposes that those organisms whose properties are relevant are
already distinguished as such specimens. What is to be explained is,
then, the ways humans generally, though not universally, are. And
among these ways are ways they may share with most specimens of some
other species, in particular those that belong to the same order
(primates) and the same class (mammals).



One should be clear what follows from this interpretation of
"human". The organisms among whom statistical frequency is
sought range over those generated after speciation around 150,000
years ago to those that will exist immediately prior to the
species' extinction. On the one hand, because of the variability
intrinsic to species, we are in the dark as to the properties that may
or may not characterise those organisms that will turn out to be the
last of the taxon. On the other hand, the time lag of around 100,000
years between the first anatomically modern humans and the general
onset of behavioural modernity around the beginning of the Upper
Palaeolithic means that there are likely to be many widespread
psychological properties of contemporary humans that were not
possessed by the majority of the species' specimens during two
thirds of the species' history. This is true even if the
practices seen as the signatures of behavioural modernity (see
 SS1.1)
 developed sporadically, disappeared and reappeared at far removed
points of time and space over tens of thousands of years before 50,000
ka (McBrearty & Brooks 2000; Sterelny 2011).



According to several authors (Machery 2008; 2018; Samuels 2012; Ramsey
2013), the expression "human nature" should be used to
group properties that are the focus of much current behavioural,
psychological and social science. However, as the cognitive and
psychological sciences are generally interested in present-day humans,
there is a mismatch between scientific focus and a grouping criterion
that takes in all the properties generally or typically instantiated
by specimens of the entire taxon. For this reason, the expression
"human nature" is likely to refer to properties of an even
more temporally restricted set of organisms belonging to the species.
That restriction can be thought of in indexical terms, i.e., as a
restriction to contemporary humans. However, some authors claim
explicitly that their accounts entail that human nature can change
(Ramsey 2013: 992; Machery 2018: 20). Human nature would then be the
object of temporally indexed investigations, as is, for example, the
weight of individual humans in everyday contexts. (Without temporal
specification, there is no determinate answer to a question such as
"How much did David Hume weigh?") An example of
Machery's is dark skin colour. This characteristic, he claims,
ceased to be a feature of human nature thus understood 7,000 years
ago, if that was when skin pigmentation became polymorphic. The
example indicates that the temporal range may be extremely narrow from
an evolutionary point of view.



Such accounts are both compatible with evolutionary theory and
coherent. However, in as far as they are mere summary or list
conceptions, it is unclear what their epistemic value might be. They
will tend to accord with everyday common sense, for which "human
nature" may in a fairly low-key sense simply be the properties
that (contemporary) humans generally tend to manifest (Roughley 2011:
16). They will also conform to one level of the expression's use
in Hume's *Treatise of Human Nature* (1739-40),
which, in an attempt to provide a human "mental geography"
(1748 [1970: 13]), lists a whole series of features, such as prejudice
(1739-40, I,iii,13), selfishness (III,ii,5), a tendency to
temporal discounting (III,ii,7) and an addiction to general rules
(III,ii,9).



Accounts of this kind have been seen as similar in content to field
guides for other animals (Machery 2008: 323; Godfrey-Smith 2014: 139).
As Hull points out, within a restricted ecological context and a short
period of evolutionary time, the ascription of readily observable
morphological or behavioural characteristics to species specimens is a
straightforward and unproblematic enterprise (Hull 1987: 175).
However, the analogy is fairly unhelpful, as the primary function of
assertions in field guides is to provide a heuristics for amateur
classification. In contrast, a list conception of the statistically
normal properties of contemporary humans presupposes identification of
the organisms in question as humans. Moreover, such accounts certainly
do not entail easy epistemic access to the properties in question,
which may only be experimentally discovered. Nevertheless, there
remains something correct about the analogy, as such accounts are a
collection of assertions linked only by the fact that they are about
the same group of organisms (Sterelny 2018: 123).



More sophisticated nature documentaries may summarise causal features
of the lives of animals belonging to specific species. An analogous
conception of human nature has also been proposed, according to which
human nature is a set of pervasive and robust causal nexuses amongst
humans. The list that picks out this set would specify causal
connections between antecedent properties, such as having been exposed
to benzene or subject to abuse as a child, and consequent properties,
such as developing cancer or being aggressive towards one's own
children (Ramsey 2013: 988ff.). Human nature thus understood would
have an explanatory component, a component internal to each item on
the list. Human nature itself would, however, not be explanatory, but
rather the label for a list of highly diverse causal connections.



An alternative way to integrate an explanatory component in a
statistical normality account involves picking out that set of
statistically common properties that have a purely evolutionary
explanation (Machery 2008; 2018). This reinterpretation of the concept
of naturalness that featured in the original package (TP1) involves a
contrast with social learning. Processes grouped together under this
latter description are taken to be alternative explanations to those
provided by evolution. However, learning plays a central role, not
only in the development of individual humans, but also in the iterated
interaction of entire populations with environments structured and
restructured through such interaction (Stotz 2010: 488ff.; Sterelny
2012: 23ff.). Hence, the proposal raises serious epistemic questions
as to how the distinction is precisely to be drawn and
operationalised. (For discussion, see Prinz 2012; Lewens 2012: 464ff.;
Ramsey 2013: 985; Machery 2018: 15ff.; Sterelny 2018: 116; Kronfeldner
2018: 147ff.).


## 4. Explanatory Human Properties



The replacement of the concept of a fully developed form with a
statistical notion yields a deflationary account of human nature with,
at most, restricted explanatory import. The correlative, explanatory
notion in the original package, that of the fully developed
form's blueprint (TP2), has to some authors seemed worth
reframing in terms made possible by advances in modern biology,
particularly in genetics.



Clearly, there must be explanations of why humans generally walk on
two legs, speak and plan many of their actions in advance.
Genealogical, or what have been called "ultimate" (Mayr)
or "historical" (Kitcher) explanations can advert to the
accumulation of coherence among entrenched, stable properties along a
lineage. These may well have resulted from selection pressures shared
by the relevant organisms (cf. Wimsatt 2003; Lewens 2009). The fact
that there are exceptions to any generalisations concerning
contemporary humans does not entail that there is no need for
explanations of such exception-allowing generalisations. Plausibly,
these general, though not universal truths will have "structural
explanations", that is, explanations in terms of underlying
structures or mechanisms (Kitcher 1986: 320; Devitt 2008: 353). These
structures, so seems, might to a significant degree be inscribed in
humans' DNA.



The precise details of rapidly developing empirical science will
improve our understanding of the extent to which there is a
determinate relationship between contemporary humans' genome and
their physical, psychological and behavioural properties. There is,
however, little plausibility that the blueprint metaphor might be
applicable to the way DNA is transcribed, translated and interacts
with its cellular environment. Such interaction is itself subject to
influence by the organism's external environment, including its
social environment (Dupre 2001: 29ff.; 2003: 111ff.; Griffiths
2011: 326; Prinz 2012: 17ff.; Griffiths & Tabery 2013: 71ff.;
Griffiths & Stotz 2013: 98ff., 143ff.). For example, the feature
of contemporary human life for which there must according to Aristotle
be some kind of blueprint, viz. rational agency, is, as Sterelny has
argued, so strongly dependent on social scaffolding that any claim to
the effect that human rationality is somehow genetically programmed
ignores the causal contributions of manifestly indispensable
environmental factors (Sterelny 2018: 120).


### 4.1 Genetically Based Psychological Adaptations?



Nevertheless, humans do generally develop a specific set of
physiological features, such as two lungs, one stomach, one pancreas
and two eyes. Moreover, having such a bodily architecture is,
according to the evidence from genetics, to a significant extent the
result of developmental programmes that ground in gene regulatory
networks (GRNs). These are stretches of non-coding DNA that regulate
gene transcription. GRNs are modular, more or less strongly entrenched
structures. The most highly conserved of these tend to be the
phylogenetically most archaic (Carroll 2000; Walsh 2006: 436ff.;
Willmore 2012: 227ff.). The GRNs responsible for basic physiological
features may be taken, in a fairly innocuous sense, to belong to an
evolved human nature.



Importantly, purely morphological features have generally not been the
explananda of accounts that have gone under the rubric "human
nature". What has frequently motivated explanatory accounts thus
labelled is the search for underlying structures responsible for
generally shared *psychological* features. "Evolutionary
Psychologists" have built a research programme around the claim
that humans share a psychological architecture that parallels that of
their physiology. This, they believe, consists of a structured set of
psychological "organs" or modules (Tooby & Cosmides
1990: 29f.; 1992: 38, 113). This architecture is, they claim, in turn
the product of developmental programmes inscribed in humans' DNA
(1992: 45). Such generally distributed developmental programmes they
label "human nature" (1990: 23).



This conception raises the question of how analogous the
characteristic physical and psychological "architectures"
are. For one thing, the physical properties that tend to appear in
such lists are far more coarse-grained than the candidates for shared
psychological properties (D. Wilson 1994: 224ff.): the claim is not
just that humans tend to have perceptual, desiderative, doxastic and
emotional capacities, but that the mental states that realise these
capacities tend to have contents of specific types. Perhaps an
architecture of the former kind--of a formal psychology--is
a plausible, if relatively unexciting candidate for the mental side of
what an evolved human nature should explain. Either way, any such
conception needs to adduce criteria for the individuation of such
"mental organs" (D. Wilson 1994: 233). Relatedly, if the
most strongly entrenched developmental programmes are the most
archaic, it follows that, although these will be species-typical, they
will not be species-specific. Programmes for the development of body
parts have been identified for higher taxa, rather than for
species.



A further issue that dogs any such attempts to explicate the
"human" dimension of human nature in terms of
developmental programmes inscribed in human DNA concerns Evolutionary
Psychologists' assertion that the programmes are the same in
every specimen of the species. This assertion goes hand in hand with
the claim that what is explained by such programmes is a deep
psychological structure that is common to almost all humans and
underlies the surface diversity of behavioural and psychological
phenomena (Tooby & Cosmides 1990: 23f.). For Evolutionary
Psychologists, the (near-)universality of both developmental
programmes and deep psychological structure has an ultimate
explanation in evolutionary processes that mark their products as
natural in the sense of TP1. Both, they claim, are adaptations. These
are features that were selected for because their possession in the
past conferred a fitness advantage on their possessors. Evolutionary
Psychologists conceive that advantage as conferred by the fulfilment
of some specific function. They summarise selection for that function
as "design", which they take to have operated equally on
all species specimens since the Pleistocene. This move reintroduces
the teleological idea of a fully developed form beyond mere
statistical normality (TP3).



This move has been extensively criticised. First, selection pressures
operate at the level of groups and hence need not lead to the same
structures in all a group's members (D. Wilson 1994: 227ff.;
Griffiths 2011: 325; Sterelny 2018: 120). Second, other evolutionary
mechanisms than natural selection might be explanatorily decisive.
Genetic drift or mutation and recombination might, for example, also
confer "naturalness" in the sense of evolutionary genesis
(Buller 2000: 436). Third, as we have every reason to assume that the
evolution of human psychology is ongoing, evolutionary biology
provides little support for the claim that particular programmes and
associated traits evolved to fixity in the Pleistocene (Buller 2000:
477ff.; Downes 2010).



Perhaps, however, there might turn out to be gene control networks
that do generally structure certain features of the psychological
development of contemporary humans (Walsh 2006: 440ff.). The quest for
such GNRs can, then, count as the search for an explanatory nature of
contemporary humans, where the explanatory function thus sought is
divorced from any classificatory role.


### 4.2 Abandoning Intrinsicality



There has, however, been a move in general philosophy of science that,
if acceptable, would transform the relationship between the taxonomic
and explanatory features of species. This move was influentially
initiated by Richard Boyd (1999a). It begins with the claim that the
attempt to define natural kinds in terms of spatiotemporally
unrestricted, intrinsic, necessary and sufficient conditions is a
hangover from empiricism that should be abandoned by realist
metaphysics. Instead, natural kinds should be understood as kinds that
support induction and explanation, where generalisations at work in
such processes need not be exceptionless. Thus understood, essences of
natural kinds, i.e., their "natures", need be neither
intrinsic nor be possessed by all and only members of the kinds.
Instead, essences consist of property clusters integrated by
stabilising mechanisms ("homeostatic property clusters",
HPCs). These are networks of causal relations such that the presence
of certain properties tends to generate or uphold others and the
workings of underlying mechanisms contribute to the same effect. Boyd
names storms, galaxies and capitalism as plausible examples (Boyd
1999b: 82ff.). However, he takes species to be the paradigmatic HPC
kinds. According to this view, the genealogical character of a
species' nature does not undermine its causal role. Rather, it
helps to explain the specific way in which the properties cohere that
make up the taxon's essence. Moreover, these can include
extrinsic properties, for example, properties of constructed niches
(Boyd 1991: 142, 1999a: 164ff.; Griffiths 1999: 219ff.; R. Wilson et
al. 2007: 202ff.).



Whether such an account can indeed adequately explain taxonomic
practice for species taxa is a question that can be left open here
(see Ereshefsky & Matthen 2005: 16ff.). By its own lights the
account does not identify conditions for belonging to a species such
as *Homo sapiens* (Samuels 2012: 25f.). Whether it enables the
identification of factors that play the explanatory roles that the
term "human nature" might be supposed to pick out is
perhaps the most interesting question. Two ways in which an account of
human nature might be developed from such a starting point have been
sketched.



According to Richard Samuels' proposal, human nature should be
understood as the empirically discoverable proximal mechanisms
responsible for psychological development and for the manifestation of
psychological capacities. These will include physiological mechanisms,
such as the development of the neural tube, as well as environmentally
scaffolded learning procedures; they will also include the various
modular systems distinguished by cognitive science, such as visual
processing and memory systems (Samuels 2012: 22ff.). Like mere list
conceptions (cf.
 SS3.2),
 such an account has a precedent in Hume, for whom human nature also
includes causal "principles" that structure operations of
the human mind (1739-40, Intro.), for example, the mechanisms of
sympathy (III,iii,1; II,ii,6). Hume, however, thought of the relevant
causal principles as intrinsic.



A second proposal, advanced by Paul Griffiths and Karola Stotz,
explicitly suggests taking explanandum and explanans to be picked out
by different uses of the expression "human nature". In both
cases, the "nature" in question is that of the taxon, not
of individual organisms. The former use simply refers to "what
human beings are like", where "human beings" means
all species specimens. Importantly, this characterisation does not aim
at shared characteristics, but is open for polymorphisms both across a
population and across life stages of individual organisms. The causal
conception of human nature, what explains this spectrum of similarity
and difference in life histories, is equated by Griffiths and Stotz
with the organism-environment system that supports human development.
It thus includes all the genetic, epigenetic and environmental
resources responsible for varying human life cycles (Griffiths 2011:
319; Stotz & Griffiths 2018, 66f.). It follows that explanatory
human nature at one point in time can be radically different from
human nature at some other point in time.



Griffiths and Stotz are clear that this account diverges significantly
from traditional accounts, as it rejects assumptions that human
development has a goal, that human nature is possessed by all and only
specimens of the species and that it consists of intrinsic properties.
They see these assumptions as features of the folk biology of human
nature that is as scientifically relevant as are folk conceptions of
heat for its scientific understanding (Stotz 2010: 488; Griffiths
2011: 319ff.; Stotz & Griffiths 2018: 60ff.). This raises the
question as to whether such a developmental systems account should not
simply advocate abandoning the term, as is suggested by Sterelny
(2018) on the basis of closely related considerations. A reason for
not doing so might lie in the fact that, as talk of "human
nature" is often practised with normative intent or at least
with normative consequences (Stotz & Griffiths 2018: 71f.), use of
the term to pick out the real, complex explanatory factors at work
might help to counter those normative uses that employ false, folk
biological assumptions.


### 4.3 Secondary Altriciality as a Game-Changer



Explanatory accounts that emphasise developmental plasticity in the
products of human DNA, in the neural architecture of the brain and in
the human mind tend to reject the assumption that explanations of what
humans are like should focus on intrinsic features. It should,
however, be noted that such accounts can be interpreted as assigning
the feature of heightened plasticity the key role in such explanations
(cf. Montagu 1956: 79). Accounts that make plasticity causally central
also raise the question as to whether there are not biological
features that in turn explain it and should therefore be assigned a
more central status in a theory of explanatory human nature.



A prime candidate for this role is what the zoologist Adolf Portmann
labelled human "secondary altriciality", a unique
constellation of features of the human neonate relative to other
primates: human neonates are, in their helplessness and possession of
a relatively undeveloped brain, neurologically and behaviourally
altricial, that is, in need of care. However they are also born with
open and fully functioning sense organs, otherwise a mark of precocial
species, in which neonates are able to fend for themselves (Portmann
1951: 44ff.). The facts that the human neonate brain is less than 30%
of the size of the adult brain and that brain development after birth
continues at the fetal rate for the first year (Walker & Ruff
1993, 227) led the anthropologist Ashley Montagu to talk of
"exterogestation" (Montagu 1961: 156). With these features
in mind, Portmann characterised the care structures required by
prolonged infant helplessness as the "social uterus"
(Portmann 1967: 330). Finally, the fact that the rapid development of
the infant brain takes place during a time in which the infant's
sense organs are open and functioning places an adaptive premium on
learning that is unparalleled among organisms (Gould 1977: 401; cf.
Stotz & Griffiths 2018: 70).



Of course, these features are themselves contingent products of
evolution that could be outlived by the species. Gould sees them as
components of a general retardation of development that has
characterised human evolution (Gould 1977: 365ff.), where
"human" should be seen as referring to the clade--all
the descendants of a common ancestor--rather than to the species.
Anthropologists estimate that secondary altriciality characterised the
lineage as from *Homo erectus* 1.5 million years ago (Rosenberg
& Trevathan 1995: 167). We are, then, dealing with a set of deeply
entrenched features, features that were in place long before
behavioural modernity.



It is conceivable that the advent of secondary altriciality was a key
transformation in generating the radical plasticity of human
development beginning with early hominins. However, as Sterelny points
out, there are serious difficulties with isolating any particular game
changer. Secondary altriciality, or the plasticity that may in part be
explained by it, would thus seem to fall victim to the same verdict as
the game changers named by the traditional human nature slogans.
However, maybe it is more plausible to think in terms of a matrix of
traits: perhaps a game-changing constellation of properties present in
the population after the split from *pan* can be shown to have
generated forms of niche construction that fed back into and modified
the original traits. These modifications may in turn have had further
psychological and behavioural consequences in steps that plausibly
brought selective advantages (Sterelny 2018: 115).


## 5. Human Nature, the Participant Perspective and Morality


### 5.1. Human Nature from a Participant Perspective



In such a culture-mind coevolutionary account, there may be a place
for the referents of some of the traditional philosophical slogans
intended to pin down "the human essence" or "human
nature"--reason, linguistic capacity (*"*the
speaking animal", Herder 1772 [2008: 97]), a more general
symbolic capacity (*animal symbolicum*, Cassirer 1944: 44),
freedom of the will (Pico della Mirandola 1486 [1965: 5]; Sartre 1946
[2007: 29, 47]), a specific, "political" form of
sociality, or a unique type of moral motivation (Hutcheson 1730:
SS15). These are likely, at best, to be the (still evolving)
products in contemporary humans of processes set in motion by a trait
constellation that includes proto-versions of (some of) these
capacities. Such a view may also be compatible with an account of
"what contemporary humans are like" that abstracts from
the evolutionary time scale of eons and focuses instead on the present
(cf. Dupre 1993: 43), whilst neither merely cataloguing widely
distributed traits
 (SS3.2)
 nor attempting explanations in terms of the human genome
 (SS4.1).
 The traditional slogans appear to be attempts to summarise some such
accounts. It seems clear, though, that their aims are significantly
different from those of the biologically, or otherwise scientifically
orientated positions thus far surveyed.



Two features of such accounts are worth emphasising, both of which we
already encountered in Aristotle's contribution to the original
package. The first involves a shift in perspective from that of the
scientific observer to that of a *participant* in a
contemporary human life form. Whereas the human--or
non-human--biologist may ask what modern humans are like, just as
they may ask what bonobos are like, the question that traditional
philosophical accounts of human nature are plausibly attempting to
answer is what it is like to live one's life as a contemporary
human. This question is likely to provoke the counter-question as to
whether there is anything that it is like to live simply as a
contemporary human, rather than as a
human-in-a-specific-historical-and-cultural context (Habermas 1958:
32; Geertz 1973: 52f.; Dupre 2003: 110f.). For the traditional
sloganeers, the answer is clearly affirmative. The second feature of
such accounts is that they tend to take it that reference to the
capacities named in the traditional slogans is in some sense
*normatively*, in particular, ethically
*significant*.



The first claim of such accounts, then, is that there is some property
of contemporary humans that is in some way descriptively or causally
central to participating in their form of life. The second is that
such participation involves subjection to normative standards rooted
in the possession of some such property. Importantly, there is a step
from the first to the second form of significance, and justification
of the step requires argument. Even from a participant perspective,
there is no automatic move from explanatory to normative
significance.



According to an "internal", participant account of human
nature, certain capacities of contemporary, perhaps modern humans
unavoidably *structure* the way they (we) live their (our)
lives. Talk of "structuring" refers to three kinds of
contributions to the matrix of capacities and dispositions that both
enable and constrain the ways humans live their lives. These are
contributions, first, to the specific shape other features of humans
lives have and, second, to the way other such features hang together
(Midgley 2000: 56ff.; Roughley 2011: 16ff.). Relatedly, they also make
possible a whole new set of practices. All three relations are
explanatory, although their explanatory role appears not necessarily
to correspond to the role corresponding features, or earlier versions
of the features, might have played in the evolutionary genealogy of
contemporary human psychology. Having linguistic capacities is a prime
candidate for the role of such a structural property: human
perception, emotion, action planning and thought are all plausibly
transformed in linguistic creatures, as are the connections between
perception and belief, and the myriad relationships between thought
and behaviour, connections exploited and deepened in a rich set of
practices unavailable to non-linguistic animals. Similar things could
be claimed for other properties named by the traditional slogans.



In contrast to the ways in which such capacities have frequently been
referred to in the slogan mode, particularly to the pathos that has
tended to accompany it, it seems highly implausible that any one such
property will stand alone as structurally significant. It is more
likely that we should be picking out a constellation of properties, a
constellation that may well include properties variants of which are
possessed by other animals. Other properties, including capacities
that may be specific to contemporary humans, such as humour, may be
less plausible candidates for a structural role.



Note that the fact that such accounts aim to answer a question asked
from the participant perspective does not rule out that the features
in question may be illuminated in their role for human
self-understanding by data from empirical science. On the contrary, it
seems highly likely that disciplines such as developmental and
comparative psychology, and neuroscience will contribute significantly
to an understanding of the possibilities and constraints inherent in
the relevant capacities and in the way they interact.


### 5.2. Human Nature and the Human *ergon*



The paradigmatic strategy for deriving ethical consequences from
claims about structural features of the human life form is the
Platonic and Aristotelian *ergon* or function argument. The
first premise of Aristotle's version (*Nicomachean
Ethics* 1097b-1098a) connects function and goodness: if the
characteristic function of an entity of a type *X* is to ph,
then a good entity of type *X* is one that phs well. Aristotle
confers plausibility on the claim by using examples such as social
roles and bodily organs. If the function of an eye as an exemplar of
its kind is to enable seeing, then a good eye is one that enables its
bearer to see well. The second premise of the argument is a claim we
encountered in
 section 1.4
 of this entry, a claim we can now see as predicating a structural
property of human life, the exercise of reason. According to this
claim, the function or end of individual humans as humans is,
depending on interpretation (Nussbaum 1995: 113ff.), either the
exercise of reason or life according to reason. If this is correct, it
follows that a good human being is one whose life centrally involves
the exercise of, or life in accordance with, reason.



In the light of the discussion so far, it ought to be clear that, as
it stands, the second premise of this argument is incompatible with
the evolutionary biology of species. It asserts that the exercise of
reason is not only the key structural property of human life, but also
the realization of the fully developed human form. No sense can be
made of this latter notion in evolutionary terms. Nevertheless, a
series of prominent contemporary ethicists--Alasdair MacIntyre
(1999), Rosalind Hursthouse (1999), Philippa Foot (2001) and Martha
Nussbaum (2006)--have all made variants of the *ergon*
argument central to their ethical theories. As each of these authors
advance some version of the second premise, it is instructive to
examine the ways in which they aim to avoid the challenge from
evolutionary biology.



Before doing so, it is first worth noting that any ethical theory or
theory of value is engaged in an enterprise that has no clear place in
an evolutionary analysis. If we want to know what goodness is or what
"good" means, evolutionary theory is not the obvious place
to look. This is particularly clear in view of the fact that
evolutionary theory operates at the level of populations (Sober 1980:
370; Walsh 2006: 434), whereas ethical theory operates, at least
primarily, at the level of individual agents. However, the specific
conflict between evolutionary biology and neo-Aristotelian ethics
results from the latter's constructive use of the concept of
species and, in particular, of a teleological conception of a fully
developed form of individual members of the species
"*qua* members of [the] species" (MacIntyre 1999:
64, 71; cf. Thompson 2008: 29; Foot 2001: 27). The characterisation of
achieving that form as fulfilling a "function", which
helps the analogy with bodily organs and social roles, is frequently
replaced in contemporary discussions by talk of
"flourishing" (Aristotle's *eudaimonia*).
Such talk more naturally suggests comparisons with the lives of other
organisms (although Aristotle himself excludes other animals from
*eudaimonia*; cf. *Nicomachean Ethics* 1009b). The
concept of flourishing in turn picks out
biological--etymologically: botanical--processes, but again
not of a sort that play a role in evolutionary theory. It also seems
primarily predicated of individual organisms. It may play a role in
ecology; it is, however, most clearly at home in practical
applications of biological knowledge, as in horticulture. In this
respect, it is comparable to the concept of health.



Neo-Aristotelians claim that to describe an organism, whether a plant
or a non-human or human animal, as flourishing is to measure it
against a standard that is specific to the species to which it
belongs. To do so is to evaluate it as a more or less good
"specimen of its species (or sub-species)" (Hursthouse
1999: 198). The key move is then to claim that moral evaluation is,
"quite seriously" (Foot 2001: 16), evaluation of the same
sort: just as a non-defective animal or plant exemplifies flourishing
within the relevant species' life form, someone who is morally
good is someone who exemplifies human flourishing, i.e., the fully
developed form of the species. This metaethical claim has provoked the
worry as to whether such attributions to other organisms are really
anything more than classifications, or at most evaluations of
"stretched and deflated" kinds that are missing the key
feature of authority that we require for genuine normativity (Lenman
2005: 46ff.).


#### 5.2.1. Sidestepping the Darwinian Challenge?



Independently of questions concerning their theory of value, ethical
Neo-Aristotelians need to respond to the question of how reference to
a fully developed form of the species can survive the challenge from
evolutionary theory. Three kinds of response may appear promising.



The *first* adverts to the plurality of forms of biological
science, claiming that there are life sciences, such as physiology,
botany, zoology and ethology in the context of which such evaluations
have a place (Hursthouse 1999: 202; 2012: 172; MacIntyre 1999: 65).
And if ethology can legitimately attribute not only characteristic
features, but also defects or flourishing to species members, in spite
of species not being natural kinds, then there is little reason why
ethics shouldn't do so too. This strategy might ground in one of
the moves sketched in
 section 3.1
 of this entry. It might be argued, with Kitcher and Dupre,
that such attributions are legitimate in other branches of biological
science because there is a plurality of species concepts, indeed of
kinds of species, where these are relative to epistemic interests. Or
the claim might simply rest on a difference in what is taken to be the
relevant time frame, where temporal relevance is indexed relative to
the present. In ethics we are, it might be claimed, interested in
humans as they are "at the moment and for a few millennia back
and for maybe not much longer in the future" (Hursthouse 2012:
171).



This move amounts to the concession that talk of "the human
species" is not to be understood literally. Whether this
concession undermines the ethical theories that use the term is
perhaps unclear. It leaves open the possibility that, as human nature
may change significantly, there may be significant changes in what it
means for humans to flourish and therefore in what is ethically
required. This might be seen as a virtue, rather than a vice of the
view.



A *second* response to the challenge from evolutionary biology
aims to draw metaphysical consequences from epistemic or semantic
claims. Michael Thompson has argued that what he calls alternatively
"the human life form" and "the human species"
is an a priori category. Thompson substantiates this claim by
examining forms of discourse touched on in
 section 3.2,
 forms of discourse that are generally taken to be of mere heuristic
importance for amateur practices of identification, viz. field guides
or animal documentaries. Statements such as "The domestic cat
has four legs, two eyes, two ears and guts in its belly", are,
Thompson claims, instances of an important kind of predication that is
neither tensed nor quantifiable. He calls these "natural
historical descriptions" or "Aristotelian
categoricals" (Thompson 2008: 64ff.). Such generic claims are
not, he argues, made false where what is predicated is less than
universal, or even statistically rare. Decisively, according to
Thompson, our access to the notion of the human life form is
non-empirical. It is, he claims, a presupposition of understanding
ourselves from the first-person perspective as breathing, eating or
feeling pain (Thompson 2004: 66ff.). Thus understood, the concept is
independent of biology and therefore, if coherent, immune to problems
raised by the Darwinian challenge.



Like Foot and Hursthouse, Thompson thinks that his Aristotelian
categoricals allow inferences to specific judgments that members of
species are defective (Thompson 2004: 54ff.; 2008: 80). He admits that
such judgments in the case of the human life form are likely to be
fraught with difficulties, but nevertheless believes that judgments of
(non-)defective realization of a life form are the model for ethical
evaluation (Thompson 2004: 30, 81f.). It may seem unclear how this
might be the case in view of the fact that access to the human life
form is supposed to be given as a presupposition of using the concept
of "I". Another worry is that the everyday understanding
on which Thompson draws may be nothing other than a branch of folk
biology. The folk tendency to ascribe teleological essences to
species, as to "races" and genders, is no indication of
the reality of such essences (Lewens 2012: 469f.; Stotz &
Griffiths 2018: 60ff.; cf. Pellegrin 1982 [1986: 16ff., 120] and
Charles 2000: 343ff., 368, on Aristotle's own orientation to the
usage of "the people").



A *final* response to evolutionary biologists' worries
aims equally to distinguish the Neo-Aristotelian account of human
nature from that of the sciences. However, it does so not by
introducing a special metaphysics of "life forms", but by
explicitly constructing an ethical concept of human nature. Martha
Nussbaum argues that the notion of human nature in play in what she
calls "Aristotelian essentialism" is, as she puts it,
"internal and evaluative". It is a hermeneutic product of
"human" self-understanding, constructed from within our
best ethical outlook: "an ethical theory of human nature",
she claims,



> 
> 
> should force us to answer for ourselves, on the basis of our very own
> ethical judgment, the question which beings are fully human ones.
> (Nussbaum 1995: 121f.; cf. Nussbaum 1992: 212ff.; 2006: 181ff.;
> McDowell 1980 [1998: 18ff.]; Hursthouse 1999: 229; 2012: 174f.)
> 
> 
> 



There can be no question here of moving from a biological
"is" to an ethical "ought"; rather, which
features are taken to belong to human nature is itself seen as the
result of ethical deliberation. Such a conception maintains the claim
that the key ethical standard is that of human flourishing. However,
it is clear that what counts as flourishing can only be specified on
the basis of ethical deliberation, understood as striving for
reflective equilibrium (Nussbaum 2006: 352ff.). In view of such a
methodological proposal, there is a serious question as to what work
is precisely done by the concept of human nature.


#### 5.2.2. Human Flourishing



Neo-Aristotelians vary in the extent to which they flesh out a
conception of species-specific flourishing. Nussbaum draws up a
comprehensive, open-ended catalogue of what she calls "the
central human capacities". These are in part picked out because
of their vulnerability to undermining or support by political
measures. They include both basic bodily needs and more specifically
human capacities, such as for humour, play, autonomy and practical
reason (Nussbaum 1992: 216ff.; 2006: 76ff.). Such a catalogue allows
the setting of three thresholds, below which a human organism would
not count as living a *human* life at all (anencephalic
children, for instance), as living a *fully human* life or as
living a *good human* life (Nussbaum 2006: 181). Nussbaum
explicitly argues that being of human parents is insufficient for
crossing the first, evaluatively set threshold. Her conception is
partly intended to provide guidelines as to how societies should
conceive disability and as to when it is appropriate to take political
measures in order to enable agents with nonstandard physical or mental
conditions to cross the second and third thresholds.



Nussbaum has been careful to insist that enabling independence, rather
than providing care, should be the prime aim. Nevertheless, the
structure of an account that insists on a "species norm",
below which humans lacking certain capacities count as less than fully
flourishing, has prompted accusations of illiberality. According to
the complaint, it disrespects the right of members of, for example,
deaf communities to set the standards for their own forms of life
(Glackin 2016: 320ff.).



Other accounts of species-specific flourishing have been considerably
more abstract. According to Hursthouse, plants flourish when their
parts and operations are well suited to the ends of individual
survival and continuance of the species. In social animals,
flourishing also tends to involve characteristic pleasure and freedom
from pain, and a contribution to appropriate functioning of relevant
social groups (Hursthouse 1999: 197ff.). The good of human character
traits conducive to pursuit of these four ends is transformed,
Hursthouse claims, by the addition of "rationality". As a
result, humans flourish when they do what they correctly take
themselves to have reason to do--under the constraint that they
do not thereby cease to foster the four ends set for other social
animals (Hursthouse 1999: 222ff.). Impersonal benevolence is, for
example, because of this constraint, unlikely to be a virtue. In such
an ethical outlook, what particular agents have reason to do is the
primary standard; it just seems to be applied under particular
constraints. A key question is thus whether the content of this
primary standard is really determined by the notion of
species-specific flourishing.



Where Hursthouse's account builds up to, and attempts to provide
a "natural" framework for, the traditional Aristotelian
*ergon* of reason, MacIntyre builds his account around the
claim that flourishing specific to the human "species" is
essentially a matter of becoming an "independent practical
reasoner" (MacIntyre 1999: 67ff.). It is because of the central
importance of reasoning that, although human flourishing shares
certain preconditions with the flourishing, say, of dolphins, it is
also vulnerable in specific ways. MacIntyre argues that particular
kinds of social practices enable the development of human reasoning
capacities and that, because independent practical reasoning is,
paradoxically, at core cooperatively developed and structured, the
general aim of human flourishing is attained by participation in
networks in local communities (MacIntyre 1999: 108).
"Independent practical reasoners" are "dependent
rational animals". MacIntyre's account thus makes room on
an explanatory level for the evolutionary insight that humans can only
become rational in a socio-cultural context which provides scaffolding
for the development and exercise of rationality
 (SS4).
 Normatively, however, this point is subordinated to the claim that,
from the point of view of participation in the contemporary human life
form, flourishing corresponds to the traditional slogan.


### 5.3. Reason as the Unique Structural Property



MacIntyre, Hursthouse and Nussbaum (Nussbaum 2006: 159f.) all aim to
locate the human capacity for reasoning within a framework that
encompasses other animals. Each argues that, although the capacities
to recognise reasons as reasons and for deliberation on their basis
transform the needs and abilities humans share with other animals, the
reasons in question remain in some way dependent on humans'
embodied and social form of life. This emphasis is intended to
distinguish an Aristotelian approach from other approaches for which
the capacity to evaluate reasons for action as reasons and to distance
oneself from ones desires is also the "central difference"
between humans and other animals (Korsgaard 2006: 104; 2018: 38ff.;
cf. MacIntyre 1999: 71ff.). According to Korsgaard's Kantian
interpretation of Aristotle's *ergon* argument, humans
cannot act without taking a normative stand on whether their desires
provide them with reasons to act. This she takes to be the key
structural feature of their life, which brings with it "a whole
new way of functioning well or badly" (Korsgaard 2018: 48; cf.
1996: 93). In such an account, "human nature" is
monistically understood as this one structural feature which is so
transformative that the concept of life applicable to organisms that
instantiate it is no longer that applicable to organisms that
don't. Only "humans" *live* their lives,
because only they possess the type of intentional control over their
bodily movements that grounds in evaluation of their actions and
self-evaluation as agents (Korsgaard 2006: 118; 2008: 141ff.; cf.
Plessner 1928 [1975: 309f.]).



We have arrived at an interpretation of the traditional slogan that
cuts it off from a metaphysics with any claims to be
"naturalistic". The claim now is that the structural
effect of the capacity for reasoning transforms those features of
humans that they share with other animals so thoroughly that those
features pale into insignificance. What is "natural" about
the capacity for reasoning for humans here is its unavoidability for
contemporary members of the species, at least for those without
serious mental disabilities. Such assertions also tend to shade into
normative claims that discount the normative status of
"animal" needs in view of the normative authority of human
reasoning (cf. McDowell 1996 [1998: 172f.]).



The most radical version of this thought leads to the claim
encountered towards the end of
 section 1.4:
 that talk of "human nature" involves no essential
reference at all to the species *Homo sapiens* or to the
hominin lineage. According to this view, the kind to which
contemporary humans belong is a kind to which entities could also
belong who have no genealogical relationship to humans. That kind is
the kind of entities that act and believe in accordance with the
reasons they take themselves to have. Aliens, synthetically created
agents and angels are further candidates for membership in the kind,
which would, unlike biological taxa, be spatiotemporally unrestricted.
The traditional term for the kind, as employed by Aquinas and Kant, is
"person" (cf. Hull 1986: 9).



Roger Scruton has recently taken this line, arguing that persons can
only be adequately understood in terms of a web of concepts
inapplicable to other animals, concepts whose applicability grounds in
an essential moral dimension of the personal life form. The concepts
pick out components of a life form that is permeated by relationships
of responsibility, as expressed in reactive attitudes such as
indignation, guilt and gratitude. Such emotions he takes to involve a
demand for accountability, and as such to be exclusive to the personal
life form, not variants of animal emotions (Scruton 2017: 52). As a
result, he claims, they situate their bearers in some sense
"outside the natural order" (Scruton 2017: 26). According
to such an account, we should embrace a methodological dualism with
respect to humans: as animals, they are subject to the same kinds of
biological explanations as all other organisms, but as persons, they
are subject to explanations that are radically different in kind.
These are explanations in terms of reasons and meanings, that is,
exercises in "Verstehen", whose applicability Scruton
takes to be independent of causal explanation (Scruton 2017: 30ff.,
46).



Such an account demonstrates with admirable clarity that there is no
necessary connection between a theory of "human nature"
and metaphysical naturalism. It also reinforces the fact, emphasised
throughout this entry, that discussions of "human nature"
require both serious conceptual spadework and explicit justification
of the use of any one such concept rather than another.