  The argument begins with the premise that things perform their function well if they have the virtue appropriate to them, and badly if they have the relevant vice (353c). It then attributes to the soul the function of “caring for things, ruling and deliberating (and all the things of this kind)”, and adds that living is also part of the function of soul (353d). This yields an interim conclusion, that a good soul cares, rules, deliberates (etc.) and lives well, whereas a bad soul does these things badly. A third premise is that justice is the virtue appropriate to the soul, injustice being its vice. Hence another interim conclusion: a just soul lives well; an unjust one, badly. But living well, says the next premise, is being happy (and living badly is being wretched). And so Socrates can draw the interim conclusion that we have encountered already, which is that the just person (the person, that is, whose soul is just) is happy, whereas the person whose soul is unjust is wretched.