In Chapter 7, I show how Aristotle appeals to the demonstrative heuristic in scrutinising Empedoclean and other elemental theories of soul that try to explain the soul’s ability to cognise. He does so in order to show that the law-like principle that ‘like cognises like’ is too limited to explain the extent of the soul’s knowledge, and that it is inconsistent with the Axiom of Causal Association. What he gains from this criticism is the idea that the domain of what we can cognise extends beyond the domain of what the material or immaterial elements, operating by the cognitive likeness principle, could know. From this Aristotle infers that the soul cannot be reduced to the elements. However, by adding two important modifications to the principle that ‘like cognises like’, I show that Aristotle imports a version of Empedocles’ likeness principle into his own hylomorphic psychology, which I call the Refined Cognitive Likeness Axiom.