 This passage comes immediately after Aristotle has stressed two related points: that the uniform parts and the instrumental parts arise simultaneously; and that even flesh and bone have a function to perform. These points are tightly connected. The defining features of tissues are not merely their affective qualities such as being hard or soft, but their biological functions as well; and their biological functions are intimately connected to their roles in constituting—and being able to play functional roles in—instrumental parts; many, if not all, of a part’s affective qualities are a consequence of its biological role.