It is impossible, that man should not be a part of Nature, or that he should be capable of undergoing no changes, save such as can be understood through his nature only as their adequate cause.
 Baruch Spinoza, Ethics (1677). copy citation

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Author Baruch Spinoza
Source Ethics
Topic change understanding
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

“when A is given, there is something else—say B—more powerful than A, and so on to infinity; thus the power of man is limited by the power of some other thing, and is infinitely surpassed by the power of external causes. Q.E.D. PROP. IV. It is impossible, that man should not be a part of Nature, or that he should be capable of undergoing no changes, save such as can be understood through his nature only as their adequate cause. Proof.—The power, whereby each particular thing, and consequently man, preserves his being, is the power of God or of Nature (I. xxiv. Coroll.) ; not in so far as it is infinite, but in so far as it can be explained by the actual human essence” source