A Different Kind of Mind?

Aristotle famously characterized human beings as animals whose soul contains a rational principle, and Scholastic philosophers codified this idea in the classical definition of man as a rational animal. ¹ It is clear that authors writing in this tradition meant to claim, not just that rationality is a characteristic trait of humankind, but that it sets us apart from other animals in a fundamental way. This is indicated in the traditional way of representing Aristotle’s picture of the natural order, the so-called “Porphyrian Tree” (Figure 10.1).