Anger is the door to all vices: if it be closed, peace is ensured within to all the virtues; if it be opened, the soul is armed for every crime.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic anger vice
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

“Further, hatred is a graver sin than anger. Therefore it should be reckoned a capital vice rather than anger. Obj. 3: Further, a gloss on Prov. 29:22, "An angry [Douay: 'passionate'] man provoketh quarrels," says: "Anger is the door to all vices: if it be closed, peace is ensured within to all the virtues; if it be opened, the soul is armed for every crime." Now no capital vice is the origin of all sins, but only of certain definite ones. Therefore anger should not be reckoned among the capital vices. On the contrary, Gregory (Moral. xxxi, 45) places anger among the capital vices.” source