“Having a body, we have seen, does not entail knowing a body. Whereas a cow automatically eats whatever grasses supply needed nutrients, people must determine for themselves what to put into their bodies, with the result that there is room to make mistakes. Mistakes arise, in part, from ignorance. Yet ignorance is not the only problem produced by this arrangement. The fact that we are not compelled by our bodies' precise needs—understood as particular kinds of food and drink, rather than food and drink tout court—allows the formation of desires that have little or nothing to do with the needs on which bodily health depends.”