Ethics, Part V, Proposition 7

We do not regard a thing as absent, by reason of the emotion wherewith we conceive it, but by reason of the body, being affected by another emotion excluding the existence of the said thing (II. xvii.). Wherefore, the emotion, which is referred to the thing which we regard as absent, is not of a nature to overcome the rest of a man's activities and power (IV. vi.), but is, on the contrary, of a nature to be in some sort controlled by the emotions, which exclude the existence of its external cause (IV. ix.). But an emotion which springs from reason is necessarily referred to the common properties of things (see the def. of reason in II. xl. note. ii.), which we always regard as present (for there can be nothing to exclude their present existence), and which we always conceive in the same manner (II. xxxviii.). Wherefore an emotion of this kind always remains the same; and consequently (V. Ax. i.) emotions, which are contrary thereto and are not kept going by their external causes, will be obliged to adapt themselves to it more and more, until they are no longer contrary to it; to this extent the emotion which springs from reason is more powerful. Q.E.D.