The attribution of nonintentional functions to parts or aspects of organic or social systems has been seen to involve the benefit of the system in question. If we ascribe a function to an item X in a system S, we assume that S is an appropriate subject of benefit, that it has a good. If we ascribe the function of pumping the blood to the heart of an animal, we assume that the animal has a good. If we ascribe the function of increasing social cohesion to the Hopi rain dance, we assume that Hopi society has a good. Function bearers are parts of wholes that have a good. This is the third metaphysical commitment we make when we give or take functional explanations. The arguments of Chapter 7, which showed that there is a categorical difference between artifactual and natural functions, also depended essentially on the presupposition that the natural systems whose parts are ascribed functions can themselves have a good. Chapter 8 argued that function bearers acquire their functions by contributing to the self-reproduction of the systems of which they are parts. And we have been treating such systems as if they had a good and that their good lies in their self-reproduction, and I have vaguely connected this with the notion of identity: Something is good for a self-reproducing system if it conduces to its self-reproduction; or to have a good is to be a self-reproducing system.