There is a growing consensus that the traditional notion of human nature has failed and that human nature needs to be reconceptualized in light of our current scientific knowledge, including the knowledge gained in genetics and evolutionary biology. In “A Plea for Human Nature,” I highlighted this need, and I engaged in this reconceptualization effort, proposing a new notion of human nature, “the nomological notion of human nature” (Machery 2008; for some more recent work, see Griffiths 2009, 2011; Stotz 2010; Samuels 2012). I am not under the illusion that my proposal is the last word on the question. Quite the opposite, in fact: Some important issues were barely touched upon, and some assertions were in need of further support (Machery ms). In “Human Nature: The Very Idea,” Tim Lewens discusses the nomological notion of human nature critically. I am grateful for Lewens's insightful article, and I examine Lewens's criticisms in this brief response.

1 Points of Agreement

Lewens holds that my proposal is “in the spirit of Hull's view” instead of disagreeing with it. While I am perfectly happy to view my work as expanding upon some inchoate suggestions made by Hull, the spirit of the contemporary effort to reconceptualize human nature is quite alien to Hull's well-known article (Hull 1986). Hull is not calling for such reconceptualization; on the contrary, he seems wary of any reference to human nature, and he would probably have preferred that people stopped talking about human nature altogether.

Lewens also criticizes the analogy I made between research on human nature and field guides used by birdwatchers to identify birds. I find his criticisms compelling, and I agree that the value of this analogy is limited.

2 Points of Disagreement

Lewens finds arbitrary my proposal that only those traits that are shared by most human beings across most cultures are constitutive of human nature to the exclusion of traits that are distinctive of various morphs in cases of polymorphism (“the universality proposal”). He also notes that evolutionary behavioral scientists seem happy to count as constitutive of human nature those traits that are only characteristic of one sex (males or females), such as the alleged cues that distinctively matter for males' mate choice, and he further argues that the pragmatic consideration I put forward for the universality proposal in “A Plea for Human Nature” (i.e., that having a notion of human nature that singles out universal traits is useful) is “weak.”

It is true that that this consideration does not carry much weight, and that stronger arguments are called for, but the universality proposal should nonetheless be upheld. Before sketching one of these arguments, I will describe what, on my view, should be said about polymorphisms. When a species includes several morphs, the traits that are characteristic of one of them are not constitutive of the nature of the species, but rather of the nature of its morphs. Thus, the alleged cues that distinctively influence males' mate choice are not constitutive of human nature, but of the nature of human males (together with the traits that are characteristic of human beings in general). Noticeably, natures form what psychologists call an “inheritance hierarchy”Footnote 1: the traits that are constitutive of the nature of the species also belong to the nature of its morphs.

In a nutshell, we should uphold the universality proposal because, if we don't—e.g., if we treat the traits that are distinctively characteristic of males and females as constitutive of human nature—then we are bound to treat the traits that are distinctive of groups such as regional variants and kin-based groups as constitutive of human nature too. It would be arbitrary to include the traits of morphs that are present throughout a species (e.g., males and females) into its nature, but not the traits that are distinctive of lineages within that species, such as subspecies that have evolved in different environments. For instance, why include the distinctive traits of male and female chimpanzees into chimpanzee nature, but not the traits that are distinctively characteristic of chimpanzee populations having evolved in different parts of Africa? Moreover, if the properties of subspecies are constitutive of the nature of a species, then it would be arbitrary not to include the distinctive properties of its regional variants, including the properties of small kin-based groups such as families, into its nature. The problem is that the resulting notion of human nature is useless since it is too inclusive, as Lewens himself recognizes. To summarize, if one wants a useful notion of human nature, upholding the universality assumption may be the only way to avoid drawing an arbitrary line.

Space limitations prevent us from considering all possible responses. Still, it is worth examining the claim that there is nothing arbitrary in drawing a line between the morphs that are present throughout the species and the lineages that have evolved in different environments because the distinctive properties of the former, but not of the latter, are found throughout the species: These traits (e.g., the distinctive traits of males and of females) are found in every environment where the species lives. However, this claim is not satisfying. It is likely that we are tempted to treat the distinctive traits of morphs present throughout the species as constitutive of human nature because of the connection between the notion of human nature and the idea of a trait being widely shared in the species. If this is the case, then why not squarely embrace the universality proposal?

Lewens also objects to the proposal that the traits that are constitutive of human nature are possessed “in virtue of evolutionary processes” (“the evolution proposal”). While Lewens's criticisms are challenging, the evolution proposal should be upheld too. Some traits are appropriate targets of ultimate and of proximate explanations, while others are only appropriate targets of proximate explanations. The belief that water is wet is an example of the latter, while the capacity to form perceptual beliefs is an example of the former. Some ultimate explanations appeal solely to cultural evolutionary processes, others solely to organic evolutionary processes, and yet others to a combination of cultural and organic evolutionary processes. Providing an ultimate explanation of our knowledge of football rules would probably appeal solely to cultural evolutionary processes. (Of course, the capacity to have beliefs would be explained by appealing to organic evolutionary processes, but this is a different explanandum.) Only those traits that are appropriate subjects of ultimate explanations that appeal to organic evolutionary processes are constitutive of human nature. Thus, the knowledge of football rules is not constitutive of human nature, and neither is imitation if Heyes is right about imitation (since, arguably, imitation is then not an appropriate target for an ultimate explanation that appeals to organic evolutionary processes).

Lewens would perhaps object that, when it comes to identifying the components of human nature, it is arbitrary to distinguish the traits that are explained by means of cultural evolutionary processes (e.g., our knowledge of football rules) from those that are explained by means of individual learning (e.g., the belief that water is wet), as well as between the traits that are explained solely by cultural evolutionary processes from those whose explanation appeals to organic evolutionary processes (e.g., the use of symmetry as a cue for mate choice). While this concern calls for a longer discussion, I will simply respond that the current attempt to reconceptualize human nature aims in part at explicating the notion of human nature that is used in the human behavioral sciences, and that the distinctions just drawn are plausibly necessary for this task.

3 Conclusion

Much work remains to be done to develop a fully satisfying and useful notion of human nature. Lewens raises some challenging issues for any notion of human nature built around the evolution and universality proposals. While more needs to be said to address his concerns fully, the objections he raises can ultimately be resisted.