 The degree of heat in a living body affects directly the specific character of the operations of the soul, making, for example, reasoning or desiring more or less principled, or more or less impulsive. Marinella asserts (citing Plutarch as her authority) that “heat is an instrument of the soul,” (1601b, 130). That is, the soul will operate in some instances through the mechanism of heat; the soul must use the body’s heat as an instrument to conduct its operations—where those operations are not only rational activities, but are also the operations of desire and appetite. Now, since these operations of the soul affect in turn the actions that a person takes, the effects of body temperature extend beyond the direct effects on the activities of the soul, to the choices and actions the person takes, causing them to be virtuous or vicious. This is borne out by what Marinella says about the relation between temperate body heat and both moral and intellectual virtues. “Little and failing heat, as in old people, is powerless for the soul’s operations,” whereas excessive heat “makes souls precipitous and unbridled,” (1601b, 130). So insufficient heat makes the soul’s operations (cognitive and moral) ineffectual, but excessive heat makes the soul’s operations unprincipled and impulsive. Now, the effects of insufficient or excessive heat are deeds, good or bad. Insufficient heat will lead to inaction, and excessive heat will lead to vicious action.