Proof.- Emotion towards a thing, which we conceive to exist, is more intense than it would be, if we conceived the thing as future V:ix.Coroll.), and is much more vehement, than if the future time be conceived as far distant from the present (IV:x.). Therefore an emotion towards a thing, whose period of existence we conceive to be far distant from the present, is far fainter, than if we conceive the thing as present; it is, nevertheless, more intense, than if we conceived the thing as contingent, wherefore an emotion towards a thing, which we regard as contingent, will be far fainter, than if we conceived the thing to be present with us. Q.E.D. Prop. XIII. Emotion towards a thing contingent, which we know not to exist in the present, is, other conditions being equal, fainter than an emotion towards a thing past. Proof.- In so far as we conceive a thing as contingent, we are not affected by the image of any other thing, which asserts the existence of the said thing (IV:Def.iii.), but, on the other hand (by hypothesis), we conceive certain things excluding its present existence. But, in so far as we conceive it in relation to time past, we are assumed to conceive something, which recalls the thing to memory, or excites the image thereof (II:xviii.&Note), which is so far the same as regarding it as present (II:xvii.Coroll.). Therefore (IV:ix.) an emotion towards a thing contingent, which we know does not exist in the present, is fainter, other conditions being equal, than an emotion towards a thing past. Q.E.D. Prop. XIV. A true knowledge of good and evil cannot check any emotion by virtue of being true, but only in so far as it is considered as an emotion. Proof.- An emotion is an idea, whereby the mind affirms of its body a greater or less force of existing than before (by the general Definition of the Emotions); therefore it has no positive quality, which can be destroyed by the presence of what is true; consequently the knowledge of good and evil cannot, by virtue oi being true, restrain any emotion. But, in so far as such knowledge is an emotion (IV:viii.) if it have more strength for restraining emotion, it will to that extent be able to restrain the given emotion. Q.E.D. Prop. XV. Desire arising from the knowledge of good and bad can be quenched or checked by many of the other desires arising from the emotions whereby we are assailed.