For an emotion is the idea of a modification of the body (by the general Def. of the Emotions) , and must therefore (by the preceding Prop.) involve some clear and distinct conception.
 Baruch Spinoza, Ethics (1677). copy citation

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Author Baruch Spinoza
Source Ethics
Topic emotions body
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

“Proof.—Properties which are common to all things can only be conceived adequately (II. Q.E.D.
Corollary.—Hence it follows that there is no emotion, whereof we cannot form some clear and distinct conception. For an emotion is the idea of a modification of the body (by the general Def. of the Emotions) , and must therefore (by the preceding Prop.) involve some clear and distinct conception.
xxxvi.) , and that we clearly and distinctly understand whatever follows from an idea, which in us is adequate (II. xl.) , it follows that everyone has the power of clearly and distinctly understanding himself and his emotions, if not absolutely, at any rate in part, and consequently of bringing it about, that he should become less subject to them.” source