In strongly Aristotelian terms, Galen insists on the importance of identifying the teleological cause, the “for the sake of the better”, in accounts of the natural world, especially those which involve animals and human beings; he also seems strongly indebted to Aristotle in his presentation of material causation, specifically of the four-quality or four-element theory which is central to his accounts of change in the natural world, the biological world in particular. These two types of causal account run through the Galenic corpus, receiving different formulations in different contexts; in §5.2 below we shall consider them in more detail, and the nature of their relationship with each other and with other causal schemes. First, we shall consider Galen’s own explicit discussions of causal schemes and causal terminology.