At the antipodes of Plato's account of virtue stand the just and the tyrannical souls. The former, of course, is ruled by reason endowed with wisdom; and the latter is ruled by a kind of erōs, which we will call erotic passion. The point of the contrast is to have a better understanding of the just soul. First, however, we need an understanding of the tyrannical. The tyrannical soul is the last in a declining series, from the philosophical through the timocratic, oligarchic, and democratic souls. At last, the tyrannical soul is the culmination of pathology in the appetitive part of the soul, the epithumētikon. To explain the various maladies arising in the appetitive part, Socrates introduces a generous variety of new kinds of appetites. In Book 8, he says the appetitive part has both necessary and unnecessary appetites (558d-559b). Using these notions, he explains the oligarchic and the democratic souls. In Book 9, Socrates introduces two more refinements in order to explain the tyrannical soul. First are the outlaw appetites, a subdivision of the unnecessary appetites (571b-d). Second is the erotic passion, itself a particularly intense sort of erōs (572e-573a). As there is a degradation in the kinds of civic rule, from oligarchy through democracy to tyranny, so there is a degradation in the forms of psychic rule associated with these various types of appetites. To understand the rule of erotic passion, we need to begin with the distinction between necessary and unnecessary appetites.