But man is like God, by his practical intellect, which is the cause of things understood, rather than by his speculative intellect, which derives its knowledge from things. Therefore man's happiness consists in an operation of the practical intellect rather than of the speculative.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic happiness understanding
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

“Whether Happiness Is an Operation of the Speculative, or of the Practical Intellect? Objection 1: It would seem that happiness is an operation of the practical intellect. For the end of every creature consists in becoming like God. But man is like God, by his practical intellect, which is the cause of things understood, rather than by his speculative intellect, which derives its knowledge from things. Therefore man's happiness consists in an operation of the practical intellect rather than of the speculative. Obj. 2: Further, happiness is man's perfect good. But the practical intellect is ordained to the good rather than the speculative intellect, which is ordained to the true. Hence we are said to be good, in reference to the perfection of the practical intellect, but not in reference to the perfection of the speculative intellect, according to which we are said to be knowing or understanding.” source