 Their account of the human soul (mind) is strongly monistic. Though they speak of the soul’s faculties, these are parts of the commanding faculty associated with the physical sense organs (Aetius, 53H). Unlike the Platonic tri-partite soul, all impulses or desires are direct functions of the rational, commanding faculty. This strongly monistic conception of the human soul has serious implications for Stoic epistemology and ethics. In the first case, our impressions of sense are affections of the commanding faculty. In mature rational animals, these impressions are thoughts, or representations with propositional content. Though a person may have no choice about whether she has a particular rational impression, there is another power of the commanding faculty which the Stoics call ‘assent’ and whether one assents to a rational impression is a matter of volition. To assent to an impression is to take its content as true. To withhold assent is to suspend judgement about whether it is true. Because both impression and assent are part of one and the same commanding faculty, there can be no conflict between separate and distinct rational and nonrational elements within oneself – a fight which reason might lose. Compare this situation with Plato’s description of the conflict between the inferior soul within us which is taken in by sensory illusions and the calculating part which is not (Rep. X, 602e). There is no reason to think that the calculating part can always win the epistemological civil war which Plato imagines to take place within us. But because the impression and assent are both aspects of one and the same commanding faculty according to the Stoics, they think that we can always avoid falling into error if only our reason is sufficiently disciplined. In a similar fashion, impulses or desires are movements of the soul toward something. In a rational creature, these are exercises of the rational faculty which do not arise without assent. Thus, a movement of the soul toward X is not automatically consequent upon the impression that X is desirable. This is what the Stoics’ opponents, the Academic Skeptics, argue against them is possible (Plutarch, 69A.) The Stoics, however, claim that there will be no impulse toward X – much less an action – unless one assents to the impression (Plutarch, 53S). The upshot of this is that all desires are not only (at least potentially) under the control of reason, they are acts of reason. Thus there could be no gap between forming the decisive judgement that one ought to do X and an effective impulse to do X.