PROP. V. The power and increase of every passion, and its persistence in existing are not defined by the power, whereby we ourselves endeavour to persist in existing, but by the power of an external cause compared with our own.

Proof.—The essence of a passion cannot be explained through our essence alone (III. Deff. i. and ii.), that is (III. vii.), the power of a passion cannot be defined by the power, whereby we ourselves endeavour to persist in existing, but (as is shown in II. xvi.) must necessarily be defined by the power of an external cause compared with our own. Q.E.D.