In Book I, chapter 1, of On the Soul Aristotle asks whether the affections of the soul belong to the soul alone or to the composite of soul and body. He takes “anger” as his instance and sets the “physicist” beside the “dialectician”, each defining it by “matter” or by “form”. The treatise is the foundation of the scholastic psychology of the “passions”, and the passage stands under this term as the place where the affections are first brought into the study of nature.
Read in contextConsequently their definitions ought to correspond, e.g. anger should be defined as a certain mode of movement of such and such a body (or part or faculty of a body) by this or that cause and for this or that end. That is precisely why the study of the soul must fall within the science of Nature, at least so far as in its affections it manifests this double character. Hence a physicist would define an affection of soul differently from a dialectician; the latter would define e.g. anger as the appetite for returning pain for pain, or something like that, while the former would define it as a boiling of the blood or warm substance surround the heart. The latter assigns the material conditions, the former the form or formulable essence; for what he states is the formulable essence of the fact, though for its actual existence there must be embodiment of it in a material such as is described by the other.
