 A potentially even more illuminating comparison emerges from the perspective of Aristotle’s theory of the four causes, where the laws are the material cause, the antecedent conditions the efficient cause, the logical relation between the explanans and the explanandum the formal cause and the explanandum the final cause (Fetzer 2000a: 113–114). There were important differences in their conceptions of law. Aristotle’s general premises were definitional, necessarily, whereas Hempel’s were not. The following figure shows the parallel.