E3P10D
Demonstration — Part III
Latin
Quicquid corpus nostrum potest destruere, in eodem dari nequit (per propositionem 5 hujus) adeoque neque ejus rei idea potest in Deo dari quatenus nostri corporis ideam habet (per corollarium propositionis 9 partis II) hoc est (per propositiones 11 et 13 partis II) ejus rei idea in nostra mente dari nequit sed contra quoniam (per propositiones 11 et 13 partis II) primum quod mentis essentiam constituit, est idea corporis actu existentis, primum et præcipuum nostræ mentis conatus est (per propositionem 7 hujus) corporis nostri existentiam affirmare atque adeo idea quæ corporis nostri existentiam negat, nostræ menti est contraria etc. Q.E.D.
English (Elwes 1883)
Whatsoever can destroy our body, cannot be postulated therein (III. v.). Therefore neither can the idea of such a thing occur in God, in so far as he has the idea of our body (II. ix. Coroll.); that is (II. xi., xiii.), the idea of that thing cannot be postulated as in our mind, but contrariwise, since (II. xi., xiii.) the first element, that constitutes the essence of the mind, is the idea of the human body as actually existing, it follows that the first and chief endeavour of our mind is the endeavour to affirm the existence of our body: thus, an idea, which negatives the existence of our body, is contrary to our mind, &c. Q.E.D.
Modern English
Whatever can destroy our body cannot exist within it (E3P5). Therefore no idea of such a thing can exist in God insofar as God has the idea of our body (E2P9C), that is, (E2P11), no idea of that thing can exist in our mind. On the contrary, since (E2P11) the first thing constituting the essence of the mind is the idea of an actually existing body, the first and principal *conatus* of our mind (E3P7) is to affirm the existence of our body. An idea that negates the existence of our body is therefore contrary to our mind, etc. Q.E.D.