But furthermore, love must needs be, absolutely speaking, stronger than hatred. Because a thing is moved to the end more strongly than to the means. Now turning away from evil is directed as a means to the gaining of good.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic evil love
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

“I answer that, It is impossible for an effect to be stronger than its cause. Now every hatred arises from some love as its cause, as above stated (A. 2). Therefore it is impossible for hatred to be stronger than love absolutely.
But furthermore, love must needs be, absolutely speaking, stronger than hatred. Because a thing is moved to the end more strongly than to the means. Now turning away from evil is directed as a means to the gaining of good. Wherefore, absolutely speaking, the soul's movement in respect of good is stronger than its movement in respect of evil.
Nevertheless hatred sometimes seems to be stronger than love, for two reasons.” source