Wherefore the intellect attains perfection, in so far as it knows the essence of a thing.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic perfection intellect
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

“First, that man is not perfectly happy, so long as something remains for him to desire and seek: secondly, that the perfection of any power is determined by the nature of its object. Now the object of the intellect is "what a thing is," i.e. the essence of a thing, according to De Anima iii, 6. Wherefore the intellect attains perfection, in so far as it knows the essence of a thing. If therefore an intellect knows the essence of some effect, whereby it is not possible to know the essence of the cause, i.e. to know of the cause "what it is"; that intellect cannot be said to reach that cause simply, although it may be able to gather from the effect the knowledge that the cause is.” source