Although virtue is essentially a perfection, it does not follow that whatever is the matter of a virtue implies perfection.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic perfection virtue
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

“There is no good counsel either in deliberating for an evil end, or in discovering evil means for attaining a good end, even as in speculative matters, there is no good reasoning either in coming to a false conclusion, or in coming to a true conclusion from false premisses through employing an unsuitable middle term. Hence both the aforesaid processes are contrary to euboulia, as the Philosopher declares (Ethic. vi, 9) . Reply Obj. 2: Although virtue is essentially a perfection, it does not follow that whatever is the matter of a virtue implies perfection. For man needs to be perfected by virtues in all his parts, and this not only as regards the acts of reason, of which counsel is one, but also as regards the passions of the sensitive appetite, which are still more imperfect.” source