In his Republic, Plato claims that we always do whatever we do in pursuit of the good. But in Book IV of the Republic, Plato shows that people can have attractions and aversive reactions at the same time toward the same objects or actions. In this essay, I argue that Plato’s recognition and use of aversion as a motivating response cannot be squared with what I call his ‘motivational monism’, that is, with the view that the pursuit of the good is the only thing that motivates us. Rather, as Plato’s own arguments show clearly, sometimes we don’t pursue what is good; instead, we act so as to avoid what is bad. I contend that this negative motivation cannot be wholly understood in terms of our positive interest in what is good.