Evil does not act, nor is it desired, except by virtue of some good joined to it
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic evil virtue
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17611/pg17611-images.html

Context

“But in these two ways evil does not effect anything of itself, that is, as a privation, but by virtue of the good annexed to it. For every action comes from some form; and everything which is desired as an end, is a perfection. And therefore, as Dionysius says (Div. Nom. iv) : "Evil does not act, nor is it desired, except by virtue of some good joined to it: while of itself it is nothing definite, and beside the scope of our will and intention." Reply Obj. 5: As was said above, the parts of the universe are ordered to each other, according as one acts on the other, and according as one is the end and exemplar of the other.” source