In this paper, I consider how each of the four main kinds of corrupt person described in Plato's Republic, Books 8-9, first comes to be. Certain passages in these books can give the impression that each person is able to determine, by a kind of rational choice, the overall government of his/her soul. However, I argue, this impression is mistaken. Upon careful examination, the text of books 8 and 9 overwhelmingly supports an alternative interpretation. According to this view, the eventual government of each person’s soul is decided by a struggle for power occurring within the person, among the soul’s parts, the outcome of which is determined by the relative strength and alignment of the competing parties. If this interpretation is correct, Plato adheres more closely to the city-soul analogy in these passages than has sometimes been thought. The ultimate origins of vice in the soul are also seen to lie squarely in upbringing and education, not in a mistaken choice of life.