Recently scholars have been claiming that Aristotle’s biological explanations treat “facts about matter”—facts such as the degree of heat or amount of fluidity in an organism’s material constitution—as explanatorily basic or “primitive.” That is, these facts about matter are taken to be unexplained, brute facts about organisms, rather than ones that are explained by the organism’s form or essence, as we would have expected from Aristotle’s general commitment to the causal and explanatory priority of form over matter. In this paper, I present three considerations for rejecting the view that facts about matter are primitive. First, there is evidence that those putative unexplained facts about degrees of heat, dryness, fluidity, etc. are, in fact, explained. Second, there are certain cases, such as human intelligence, where it would be quite implausible to consider the explanation in terms of degrees of heat to be starting from what Aristotle considers primitive facts. Third, the idea that facts about matter are as explanatorily primitive as facts about form requires a particular conception of the causal processes that the explanations mirror. But this conception of the causal processes conflicts with the way Aristotle characterizes them in Generation of Animals. There, heat is not treated as a causal factor that works “independently” of soul. In my view, these three considerations provide compelling reason to reject the claim that Aristotle’s biology treats facts about matter as primitive.