THE INTELLECT OF ANIMALS: RATIONAL OR IRRATIONAL?
Alcmaeon of Croton in southern Italy (c.5th century BCE), famous for his researches on the human sense organs, especially the eye, is widely held to be the earliest Greek thinker who drew a sharp distinction between the intellectual capacities of human and non-human animals, and in so doing, he inaugurated the belief that man alone of animals is rational, a notion that became a fundamental assumption in much of subsequent classical speculation on animals. Likewise his distinction between understanding (xunesis) and perception (aisthe¯sis) would enjoy a long life in Greco-Roman thought. The natural consequence of an absence of rational capacity in non-human animals is, in Alcmaeon’s view, a lack of language and an inability to advance culturally. It is reasonable to assume that Alcmaeon’s researches on the human sense organs influenced his conclusions on animal mentality. The following statement on his views is derived from the treatise On the Senses by Theophrastus.