Abstract

The science of the soul exceeds all other parts of philosophy not only in “dignity and exactness”, but also in “usefulness, necessity, charm, and, above all, in difficulty”.1 As the body is the subject of health and disease, so too the soul is the subject of virtue and vice; and just as the physician must devote great effort to knowing the body, anyone who treats morals “must take care to have a clear understanding of things pertaining to the scientia de anima”.2 To be mistaken about the soul, in the way of materialists or the impious Averroes, is to leave “the good without reward, and evil without punishment”, and thus to “uproot all good morals, all laws and Republics”.3 The study of the soul is inescapably a prolegomenon to moral philosophy and to theology. But because it studies what is common to all living things, the science of the soul also prepares the way for the study of particular plants and animals, just as physics precedes the study of elements and mixtures.4 The natural philosopher deals with six kinds of bodies: the simple incorruptible bodies of the heavens, the simple but corruptible terrestrial elements, imperfect mixtures (ice, comets), perfect inanimate mixtures (metals and pre-.