For our will to be happy does not appertain to free-will, but to natural instinct.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic instinct
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

“"The Holy Spirit divideth unto each one as He will, namely, according to the free choice of the will, not in obedience to necessity." I answer that, We have free-will with respect to what we will not of necessity, nor by natural instinct. For our will to be happy does not appertain to free-will, but to natural instinct. Hence other animals, that are moved to act by natural instinct, are not said to be moved by free-will. Since then God necessarily wills His own goodness, but other things not necessarily, as shown above” source