A rational power is not to be directed to all opposite purposes, but to those which are contained under its proper object; for no power seeks other than its proper object.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic power purpose
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

“for it is in this sense that we are now speaking of the will. On the other hand, the shunning of evil is better described as "nolition": wherefore, just as volition is of good, so nolition is of evil. Reply Obj. 2: A rational power is not to be directed to all opposite purposes, but to those which are contained under its proper object; for no power seeks other than its proper object. Now, the object of the will is good. Wherefore the will can be directed to such opposite purposes as are contained under good, such as to be moved or to be at rest, to speak or to be silent, and such like:” source