P2: We are acted on, insofar as we are a part of Nature, which cannot be conceived through itself, without the others.

Dem.: We say that we are acted on when something arises in us of which we are only the partial cause (by IIID2), i.e. (by IIID1), something that cannot be deduced from the laws of our nature alone. Therefore, we are acted on insofar as we are a part of Nature, which cannot be conceived through itself without the others, q.e.d.