Obj. 2: Further, desire is a passion. But we love some because we desire to receive something from them: as happens in every friendship based on usefulness. Therefore another passion is a cause of love.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic friendship usefulness
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

“Objection 1: It would seem that some other passion can be the cause of love. For the Philosopher (Ethic. viii, 3) says that some are loved for the sake of the pleasure they give. But pleasure is a passion. Therefore another passion is a cause of love.
Obj. 2: Further, desire is a passion. But we love some because we desire to receive something from them: as happens in every friendship based on usefulness. Therefore another passion is a cause of love. Obj. 3: Further, Augustine says (De Trin. x, 1) : "When we have no hope of getting a thing, we love it but half-heartedly or not at all, even if we see how beautiful it is." Therefore hope too is a cause of love.
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