Love, however, regards good universally, whether possessed or not. Hence love is naturally the first act of the will and appetite; for which reason all the other appetite movements presuppose love, as their root and origin.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic love origin
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17611/pg17611-images.html

Context

“Now there are certain acts of the will and appetite that regard good under some special condition, as joy and delight regard good present and possessed; whereas desire and hope regard good not as yet possessed. Love, however, regards good universally, whether possessed or not. Hence love is naturally the first act of the will and appetite; for which reason all the other appetite movements presuppose love, as their root and origin. For nobody desires anything nor rejoices in anything, except as a good that is loved: nor is anything an object of hate except as opposed to the object of love. Similarly, it is clear that sorrow, and other things like to it, must be referred to love as to their first principle.” source