Happiness is consummate perfection, which excludes every defect from the happy.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic perfection happiness
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

“Therefore it seems unreasonable that as time goes on, man should pass from happiness to misery, and vice versa; because such like vicissitudes of time can only be for such things as are subject to time and movement. Reply Obj. 1: Happiness is consummate perfection, which excludes every defect from the happy. And therefore whoever has happiness has it altogether unchangeably: this is done by the Divine power, which raises man to the participation of eternity which transcends all change. Reply Obj. 2: The will can be directed to opposites, in things which are ordained to the end;” source