Animal Psychology and Human Nature: A Historical Perspective

In general, our concepts take shape by way of contrast. Geoffrey Lloyd commented almost 60 years ago on “the remarkable prevalence of theories based on opposition in so many societies at different stages of technological development,” and he illustrated in detail the tendency of the ancient Greeks to think in binary pairs. One fundamental distinction, found in a wide variety of cultures, is that between human beings and other animals, or, more simply, between humans and animals, which serves to identify, define, and privilege our own nature as a species. Classical Greek classifications do not invariably take the form of simple polarities, to be sure; thus, one might locate humanity within the ternary taxonomy of plants, animals, and human beings, or in the alternative triad of animals, human beings, and gods, where humanity occupies the middle tier. But whatever the larger paradigm, the essential differential between human beings and other animals was the presence or absence of reason. Plants, in Aristotle’s schema, possess a vegetative soul, which is to say, the capacity to grow and develop; animals have, in addition, the faculty of perception; but human beings are unique in possessing, in addition to these two parts of the psyche, reason or, in Greek, logos, a trait that we share with the gods (they differ from us in being immortal).