4p7d.md (1134B)
1 Emotion, in so far as it is referred to the mind, is 2 an idea, whereby the mind affirms of its body a greater or less 3 force of existence than before (cf. the general Definition of the 4 Emotions at the end of Part III.). When, therefore, the mind is 5 assailed by any emotion, the body is at the same time affected 6 with a modification whereby its power of activity is increased or 7 diminished. Now this modification of the body (IV. v.) receives 8 from its cause the force for persistence in its being; which 9 force can only be checked or destroyed by a bodily cause (II. 10 vi.), in virtue of the body being affected with a modification 11 contrary to (III. v.) and stronger than itself (IV. Ax.); 12 wherefore (II. xii.) the mind is affected by the idea of a 13 modification contrary to, and stronger than the former 14 modification, in other words, (by the general definition of the 15 emotions) the mind will be affected by an emotion contrary to and 16 stronger than the former emotion, which will exclude or destroy 17 the existence of the former emotion; thus an emotion cannot be 18 destroyed nor controlled except by a contrary and stronger 19 emotion. Q.E.D. 20 21