Now sin consists in doing what is not right, and in having a will inclined to evil. Therefore God is to man a cause of sin.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic evil sin
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17897/pg17897-images.html

Context

“1:28) : "God delivered them up to a reprobate sense, to do those things which are not right [Douay: 'convenient'] ," and a gloss comments on this by saying that "God works in men's hearts, by inclining their wills to whatever He wills, whether to good or to evil." Now sin consists in doing what is not right, and in having a will inclined to evil. Therefore God is to man a cause of sin. Obj. 2: Further, it is written (Wis. 14:11) : "The creatures of God are turned to an abomination; and a temptation to the souls of men." But a temptation usually denotes a provocation to sin. Since therefore creatures were made by God alone, as was established in the First Part (Q. 44, A. 1) , it seems that God is a cause of sin, by provoking man to sin.
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