Another proof.—The potentiality of non—existence is a negation of power, and contrariwise the potentiality of existence is a power, as is obvious.
 Baruch Spinoza, Ethics (1677). copy citation

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Author Baruch Spinoza
Source Ethics
Topic existence power
Date 1677
Language English
Reference
Note Translated by R. H. M. Elwes
Weblink http://www.gutenberg.org/files/3800/3800-h/3800-h.htm

Context

“To make such an affirmation about a being absolutely infinite and supremely perfect is absurd; therefore, neither in the nature of God, nor externally to his nature, can a cause or reason be assigned which would annul his existence. Therefore, God necessarily exists. Q.E.D.
Another proof.—The potentiality of non—existence is a negation of power, and contrariwise the potentiality of existence is a power, as is obvious. If, then, that which necessarily exists is nothing but finite beings, such finite beings are more powerful than a being absolutely infinite, which is obviously absurd; therefore, either nothing exists, or else a being absolutely infinite necessarily exists also.” source