 Clearly, the Stoic account of virtue and happiness depends on their theory about human nature. For Aristotle, virtue is perfection of the human function and the Stoics follow in this line of thinking. While their notion of virtue builds on their notion of the underlying human nature, their account of the perfection of human nature is more complex than Aristotle’s. It includes accommodation to the nature of the universe. Virtue is the perfection of human nature that makes it harmonious with the workings of fate, i.e. with Zeus’s overall plan, regarded as the ineluctable, though providential, cause of what happens in the world at large.