Man is master of his actions through the judgment of his reason, wherefore as to the movements that forestall that judgment, it is not in man's power to prevent them as a whole, i.e.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic action power
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“that "it is he who is angry in a certain way, that is praised or blamed." Reply Obj. 2: The angry man desires the evil of another, not for its own sake but for the sake of revenge, towards which his appetite turns as to a mutable good. Reply Obj. 3: Man is master of his actions through the judgment of his reason, wherefore as to the movements that forestall that judgment, it is not in man's power to prevent them as a whole, i.e. so that none of them arise, although his reason is able to check each one, if it arise. Accordingly it is stated that the movement of anger is not in man's power, to the extent namely that no such movement arise.” source