One might well wonder whether there is such a thing as ‘Aristotle’s anthropology’. Isn’t the title a blatant anachronism? The term ‘anthropology’ was not in use in ancient philosophy. And Aristotle might have resisted the label for philosophical reasons, too. Let us begin by addressing these concerns.

Aristotle establishes in this passage a strong link between a substance’s ergon and its aretē.2 Ergon is commonly translated as ‘function’.3 In many cases, it is even conceived of as something’s function or purpose in the literal sense. At least this is how Socrates appears to define the term at the end of the Republic, book I, claiming that a substance’s ergon refers to the work for which the substance is the sole or best instrument (352e and 353a). Socrates’ reference to the pruning knife to cut vines is the paradigm case. While their shoots could also be cut with a carving knife, or a chisel, or many other tools, Socrates explains how no tool does it better than the pruning knife, which is made for the purpose. Thus, according to him, we are entitled to define the ergon or function of the pruning knife to be the act of pruning. As Socrates further states (353b), everything that has an ergon also has a distinct virtue (aretē) or vice (kakia). While it is through its virtue that it performs its ergon well, the opposed vice makes it perform its ergon poorly (353c). Socrates claims this model holds not only for artefacts such as the pruning knife, but more generally: In the same way it is attributed to the knife, it is also attributed to the eye, the horse, and the human being. Since artefacts are considered paradigmatic, we may call the Socratic model the functionalist conception of virtue. Virtue here means a substance’s fitness to serve a distinct purpose that is assigned to it; it means aptitude, serviceability, or even instrumentality.4

According to a philosophical commonplace, Aristotle defined human beings as rational animals. When one takes a closer look at the surviving texts, however, it is surprisingly hard to find such a definition. Of course, Aristotle repeatedly stresses that he regards rationality as the crucial differentiating characteristic of human beings, but he nowhere defines the essence of what it is to be human in these terms. What is more, Aristotle’s abundant remarks about human nature are scattered throughout his texts, and he offers no systematic treatise on human beings.

The claim that human beings are by nature political animals is one of the most fundamental of Aristotle’s Politics, and, understandably, it has received a lot of attention.1 One very interesting, and fruitful, trend has appealed to the biological works to illuminate this famous thesis.2 This strategy has brought to light a broad conception of politicality which is exhibited by humans and other gregarious animals, including bees, wasps, ants, and cranes.3 As scholars have rightly emphasised, political animals in the broad sense collectively pursue a common end via a differentiation of roles or tasks. Different broadly political species have different common ends. Bees promote the good of the hive, wasps that of the nest, and so on. Nonetheless, every broadly political species has a shared end – really, a shared way of life – that all of its members promote in different ways. This is true of humans, although their way of life specifically involves forming and sustaining poleis, which makes them political in another, narrower, sense as well.4

If someone has considered the study of the other animals to lack value, he ought to think the same thing about himself as well; for it is impossible to look at the parts from which mankind has been constituted—blood, flesh, bones, blood vessels, and other such parts—without considerable disgust.

Human beings are not the only social animals, according to Aristotle. He doesn’t even think they are the only political animals. And in the beginning of book 8 of the Nicomachean Ethics, he suggests that non-human animals can also be friends with each other: most of them entertain friendships with their young, as well as with other members of their own species.1 So, is friendship not uniquely human either?