P3: The force by which a man perseveres in existing is limited, and infinitely surpassed by the power of external causes.

Dem.: This is evident from A1. For given a man, there is something else, say A, more powerful. And given A, there is something else again, say B, more powerful than A, and so on, to infinity. Therefore the power of man is limited by the power of another thing and infinitely surpassed by the power of external causes, q.e.d.