The act of human understanding in ourselves is not the substance itself of the intellect
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic intellect acts
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

“and the Word Himself proceeding is called the Son. Reply Obj. 1: This objection is based on the idea of generation in the first sense, importing the issuing forth from potentiality to act; in which sense it is not found in God. Reply Obj. 2: The act of human understanding in ourselves is not the substance itself of the intellect; hence the word which proceeds within us by intelligible operation is not of the same nature as the source whence it proceeds; so the idea of generation cannot be properly and fully applied to it. But the divine act of intelligence is the very substance itself of the one who understands” source