Love, however, even by reason of its own species, is capable of reflecting on itself, because it is a spontaneous movement of the lover towards the beloved, wherefore from the moment a man loves, he loves himself to love.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic love reason
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

“for since the object of the will is the universal good, whatever has the aspect of good, can be the object of an act of the will: and since to will is itself a good, man can will himself to will. Even so the intellect, whose object is the true, understands that it understands, because this again is something true. Love, however, even by reason of its own species, is capable of reflecting on itself, because it is a spontaneous movement of the lover towards the beloved, wherefore from the moment a man loves, he loves himself to love. Yet charity is not love simply, but has the nature of friendship, as stated above (Q. 23, A. 1) . Now by friendship a thing is loved in two ways: first, as the friend for whom we have friendship, and to whom we wish good things:” source