PA 1: The conditions of belonging to the species homo sapiens
The first, biological use of the term `human nature´ picks out the conditions that have to be satisfied for an organism to be a human animal. The philosophy of human nature in this sense is a branch of the philosophy of biology. Understanding human nature here, then, means understanding the concept of species as applied to human animals. If one of the genealogical conceptions of species as particular segments of the phylogenetic tree is correct, then the conditions of belonging to the species are plausibly conditions of being one of its parts, rather than one of its members. This would, moreover, appear to exclude human nature in this first sense from being the basis of substantial claims within PA 2, 3 and 4.
PA 2: Human naturalness
The second usage picks out what is natural about members of the species, what we can also call `human naturalness´. Of interest here is the extent to which features of humans can count as given prior to human intervention, rather than as products of human action. The question can be put pointedly by asking what role the concept of naturalness can have in the face of the ethological phenomenon of secondary altriciality, that is, of the extensive shaping of the plastic neonate brain in interaction with primary caregivers.
Two sorts of response seem in order: First, it is important to recognize that the notion of human nature in play is, in contrast to the biological concept, gradual in character: naturalness comes in degrees. Second, in as far as humans can be said to possess features that are natural, the features in question are likely to differ, depending on the point in an individual's development at which they are to be ascribed. As culture and convention impinge on infants from the moment of birth, we may have good reason to focus on the specified concept of a natal human nature, which picks out the natural properties and dispositions possessed by humans when they are born. Much controversy in philosophy, psychology and sociology has raged around the extent to which features of a universal natal human nature in this second sense should be seen as responsible for aspects of the lives of mature humans or of the cultures and conventions that provide frameworks for those lives.
PA 3: The set of formal psychological features characteristic of the human life form
The third and fourth salient uses of the expression `human nature´ pick out features that are in some way central to the human life form, where the human life form is that form of life characteristic of the organisms identified by the criteria constitutive of human nature in the first sense. We should, I think, distinguish two kinds of centrality thus picked out and to which two further fields of anthropological inquiry correspond. In both cases, the starting point is an everyday use of the term that in itself is philosophically distinctly underwhelming. Talk of `human nature´ crops up with some frequency in everyday assertions such as "It's human nature to be selfish" or "The impulse to help the suffering is part of our nature".
A first reason why platitudes of this kind are interesting in our context is that the phenomena they pick out - altruism, egoism, partiality, morality, cruelty, rationality, weakness of will, self-deception - all presuppose a structure of basic psychological features common to human persons. The structure presupposed involves perceptual capacities, dispositions to hedonic experience, wants, beliefs, emotions, judgements, intentions. We can thus say that it is human nature to live a life orientated in the medium of psychological states, events and processes of these kinds. Because this characterisation says nothing about the contents of the relevant psychological states, we can think of it as employing a formal concept of human nature.
The third area of philosophical anthropology is thus that of the philosophy of psychology, in as far as it is approached from a specific kind of perspective. The anthropological take involves three specifications, one negative and two positive: a) In contrast to much main-stream work in this area, it assigns no particular priority to what used to be called `the mind-body problem´. b) Its analyses of the various psychological phenomena are conducted with a view to understanding the ways in which the phenomena hang together in a characteristic formal structure. Empirical work on the development of these features and on pathologies in which some such feature is missing is particularly important in this context. c) An important methodological feature of the attempt to achieve that understanding is the comparison with relevant - psychological or other - capacities of nonhuman animals. Here again, philosophical anthropology is impossible without detailed attention to empirical work, in this case in psychology and ethology.
PA 4: The structural properties of the specifically human life form
A final concept of human nature results from the attempt rationally to reconstruct the rather emphatic, traditional talk of `what it is that makes us human´, an idiom in which talk of `nature´ is often replaced by talk of `essence´. Our proposal is that we should understand such talk as naming structural properties of the specifically human life form. The idea is that one or more of the features that can be picked out by platitudes of the kind mentioned above may be pre-eminently responsible for the particular way in which the human life form hangs together.
Philosophy has proposed a number of candidates for this role over the centuries, often failing to distinguish the explanatory question from the further question as to the value of the candidates. Reason has traditionally been seen as the human property that permeates our entire life form, making possible specific variants of such traits as sociality, self-interest, virtue and aggression. Freedom of the will, language and most recently collective intentionality are further features that have been assigned that role. Whether any single property can fill this role, whether we shouldn't think in terms of a constellation of such structural properties and, if so, how precisely they fulfil this structuring function are all central questions for philosophical anthropology in this final sense.
For more on these distinctions and their consequences, see: