Aristotle's view of the interdependency of explanation and definition rests on a metaphysical thesis: essences are what determine the nature of kinds in such a way as (1) to make their causal structure completely intelligible to us and (2) to locate them in their own distinctive niche in a nexus of genera and species. We can rationally base our understanding of the first principles of science (nous) on our understanding of this causally based pattern of kinds. The world, so understood, contains its own intelligible structure, which Aristotle identifies with the Active Intellect.
Keywords: Active Intellect, Aristotle, causation, co-determination, definition, essence, explanation, first principles, natural kinds, nous