 The immaterial human mind, as Aquinas understands it, is not just the intellect. The mind is an ensemble of three discrete powers, agent and possible intellect working in conjunction with the will. The rise of the will as a faculty of the soul is a distinctively medieval idea, but has strong roots in Augustine and, before him, in late  Stoicism.  These late-ancient sources had ascribed a prominent role in human agency to desire (appetitus) or volition (voluntas), and particularly to those desires that we endorse as our own, and which thus give rise to voluntary action. Among these earlier authors, our will is conceived of as something that we need to control, if we are to lead our lives as we should. By Aquinas’s time, however, the will (voluntas) had come to be identified not just as a power of the soul but as the power that is principally in control of human agency, directing both our thoughts and our actions. Thus, whereas Augustine and  Boethius  had wondered about how we have free choice (liberum arbitrium) over our wills, Aquinas identifies the two, concluding that “the will and free choice are not two powers, but one” (ST 1a 83.4c). He was by no means the first to conceive of the power of will in this way, but the cogency and influence of his account ensured that this framework would dominate later discussions.