Aristotle on Principles as Elements

In his discussion of the four causes, Aristotle claims that ‘the hypotheses are material causes of the conclusion’ (Physics 2. 3, Metaphysics Δ 2). This claim has puzzled commentators since antiquity. It is usually taken to mean that the premisses of any deduction are material causes of the conclusion. By contrast, I argue that the claim does not apply to deductions in general but only to scientific demonstrations. For Aristotle, the theorems of a given science are composites consisting of the indemonstrable premisses from which they are demonstrated. Accordingly, these premisses are elements, and hence material causes, of the theorems. In this way, Aristotle’s claim can be shown to be well-motivated and illuminating.