But the first alternative is absurd (by the last Prop., the proof of which is universal, and can be applied to all individual things).
Therefore, if it be possible, that man should not be capable of undergoing any changes, save such as can be explained solely through his own nature, and consequently that he must always (as we have shown) necessarily exist; such a result must follow from the infinite power of God, and consequently (I.xvi.) from the necessity of the divine nature, in so far as it is regarded as affected by the idea of any given man, the whole order of nature as conceived under the attributes of extension and thought must be deducible.

It would therefore follow (I.xxi.) that man is infinite, which (by the first part of this proof) is absurd.

It is, therefore, impossible, that man should not undergo any changes save those whereof he is the adequate cause.

Q.E.D.
Corollary .-- Hence it follows, that man is necessarily always a prey to his passions, that he follows and obeys the general order of nature, and that he accommodates himself thereto, as much as the nature of things demands.
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.