Virtues are proportionately equal in one and the same subject: yet one virtue surpasses another in excellence according to its species
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic virtue species
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

“To commit sin is unlawful on account of some inordinateness therein: wherefore those which contain a greater inordinateness are more unlawful, and consequently graver sins. Reply Obj. 2: This argument looks upon sin as though it were a pure privation. Reply Obj. 3: Virtues are proportionately equal in one and the same subject: yet one virtue surpasses another in excellence according to its species; and again, one man is more virtuous than another, in the same species of virtue, as stated above (Q. 66, AA. 1, 2) . Moreover, even if virtues were equal, it would not follow that vices are equal, since virtues are connected, and vices or sins are not.” source