E4P7D
Demonstration — Part IV
Latin
Affectus quatenus ad mentem refertur est idea qua mens majorem vel minorem sui corporis existendi vim quam antea affirmat (per generalem affectuum definitionem quæ reperitur sub finem tertiæ partis). Cum igitur mens aliquo affectu conflictatur, corpus afficitur simul affectione qua ejus agendi potentia augetur vel minuitur. Porro hæc corporis affectio (per propositionem 5 hujus) vim a sua causa accipit perseverandi in suo esse; quæ proinde nec coerceri nec tolli potest nisi a causa corporea (per propositionem 6 partis II) quæ corpus afficiat affectione illi contraria (per propositionem 5 partis III) et fortiore (per axioma hujus) atque adeo (per propositionem 12 partis II) mens afficietur idea affectionis fortioris et contrariæ priori hoc est (per generalem affectuum definitionem) mens afficietur affectu fortiori et contrario priori qui scilicet prioris existentiam secludet vel tollet ac proinde affectus nec tolli nec coerceri potest nisi per affectum contrarium et fortiorem. Q.E.D.
English (Elwes 1883)
Emotion, in so far as it is referred to the mind, is an idea, whereby the mind affirms of its body a greater or less force of existence than before (cf. the general Definition of the Emotions at the end of Part III.). When, therefore, the mind is assailed by any emotion, the body is at the same time affected with a modification whereby its power of activity is increased or diminished. Now this modification of the body (IV. v.) receives from its cause the force for persistence in its being; which force can only be checked or destroyed by a bodily cause (II. vi.), in virtue of the body being affected with a modification contrary to (III. v.) and stronger than itself (IV. Ax.); wherefore (II. xii.) the mind is affected by the idea of a modification contrary to, and stronger than the former modification, in other words, (by the general definition of the emotions) the mind will be affected by an emotion contrary to and stronger than the former emotion, which will exclude or destroy the existence of the former emotion; thus an emotion cannot be destroyed nor controlled except by a contrary and stronger emotion. Q.E.D.
Modern English
An affect, insofar as it is referred to the mind, is an idea by which the mind affirms a greater or lesser force of existence of its body than before (E3DA49). When the mind is in the grip of some affect, the body is at the same time affected with an affection by which its power of acting is increased or diminished. This affection of the body (E4P5) receives from its cause a force for persisting in its being. That force can only be restrained or destroyed by a bodily cause (E2P6) that affects the body with an affection contrary to it (E3P5) and stronger (E4A1). So the mind (E2P12) will be affected by the idea of an affection that is stronger than and contrary to the previous one — that is (E3DA49), by an affect stronger than and contrary to the previous one — which will exclude or destroy the existence of the previous affect. An affect therefore cannot be destroyed or restrained except by a contrary and stronger affect. Q.E.D.