P19: The human Mind does not know the human Body itself, nor does it know that it exists, except through ideas of affections by which the Body is affected.

Dem.: For the human Mind is the idea itself, or knowledge of the human Body (by P13), which (by P9) is indeed in God/Nature insofar as he is considered to be affected by another idea of a singular thing, or because (by Post. 4) the human Body requires a great many bodies by which it is, as it were, continually regenerated; and {NS: because} the order and connection of ideas is (by P7) the same as the order and connection of causes,46 this idea will be in God/Nature insofar as he is considered to be affected by the ideas of a great many singular things. Therefore, God/Nature has the idea of the human Body, or knows the human Body, insofar as he is affected by a great many other ideas, and not insofar as he constitutes the nature of the human Mind, i.e. (by P11 C ), the human Mind does not know the human Body. But the ideas of affections of the Body are in God/Nature insofar as he constitutes the nature of the human Mind, or the human Mind perceives the same affections (by P12), and consequently (by P16) the human Body itself, as actually existing (by P17). Therefore to that extent only, the human Mind perceives the human Body itself, q.e.d.