I examine the status of Aristotle’s science of soul and argue that it is trans-generic in the way that Aristotle's universal mathematics is. For just as the branches of the latter differ considerably, so too do the sciences of life: botany, zoology, psychology, and (in Aristotle’s view) astronomy and theology. Discovering the correct definition of soul, which is their starting point or first principle, as with other scientific starting points, involves both induction and dialectic. Induction uses scientific observation of living things to move toward this starting point. Dialectic enables the scientist to assemble endoxa, or reputable beliefs, that allow us to solve each puzzle (aporia) that clouds our understanding (nous) of the starting point that induction enables us to reach.