Full Idea
That a man, from the necessity of his own nature, should endeavour to become non-existent, is as impossible as that something should be made out of nothing.
Gist of Idea
It is impossible that the necessity of a person's nature should produce a desire for non-existence
Source
Baruch de Spinoza (The Ethics [1675], IV Pr 20)
Book Reference
Spinoza,Benedict de: 'Ethics, Improvement of Understanding, Letters', ed/tr. Elwes,R [Dover 1955], p.203
A Reaction
At first glance this is very paradoxical, but it fits with evolutionary theory, which seems to make it almost inconceivable to naturally desire suicide. The desire to live is universal, and only circumstances can create an artifiical contradictory desire.