Spinoza's Ethics: III.P10

Idea quæ corporis nostri existentiam secludit in nostra mente dari nequit sed eidem est contraria.

An idea which cuts off the existence of our body is not able to be in our mind but is contrary to it.

DEMONSTRATIO: 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. 

Whatever our body is able to destroy, is not able to be in the same (by IIIP5) and to this extent is not able to be the idea of this thing to be in God insofar as it has the idea of our body (by IIP9C), that is (by IIP11 and IIP13) is not able to be the idea of this thing in our mind but the opposite since (by IIP11 and IIP13) first which establishes the essence of the mind is the idea of the existence of the body in actuality, first and particular is the trying of our mind (by IIIP7) to affirm the existence of our body and to such an extent the idea which denies the existence of our body is contrary of our mind, etc.

This proposition raises some related issues. The first one is the contemplation of our own death. If Spinoza is correct, then the inability to conceive of not existing would naturally give rise to all kinds of imaginations - such as eternal life or heaven. Our mind's conatus seems to naturally resist such notions. Further, the related concept of suicide seems particularly difficult. Suicide occurs when life is too painful to live and the alternative appears better. But if the alternative is non-existence, how is it able to be in the mind? Finally, related to both of these issues, Spinoza raises the issue that the mind has unity, but certainly we have fragmentary self-states and schizophrenia is real. Perhaps he is identifying states which are unhealthy - those that do not try to affirm the existence of our body or our life affirming. These issues need more clarity to fully grasp his message.