Hence just as the appetite is the principle of human acts, in so far as it partakes of reason, so are moral habits to be considered virtues in so far as they are in conformity with reason.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic conformity virtue
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

“Accordingly for a man to do a good deed, it is requisite not only that his reason be well disposed by means of a habit of intellectual virtue; but also that his appetite be well disposed by means of a habit of moral virtue. And so moral differs from intellectual virtue, even as the appetite differs from the reason. Hence just as the appetite is the principle of human acts, in so far as it partakes of reason, so are moral habits to be considered virtues in so far as they are in conformity with reason. Reply Obj. 1: Augustine usually applies the term "art" to any form of right reason; in which sense art includes prudence which is the right reason about things to be done, even as art is the right reason about things to be made.” source