The created essence is compared to the essence of God as the imperfect to the perfect act.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic God essence
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

“We must say therefore that God not only knows that all things are in Himself; but by the fact that they are in Him, He knows them in their own nature and all the more perfectly, the more perfectly each one is in Him. Reply Obj. 2: The created essence is compared to the essence of God as the imperfect to the perfect act. Therefore the created essence cannot sufficiently lead us to the knowledge of the divine essence, but rather the converse. Reply Obj. 3: The same thing cannot be taken in an equal manner as the ratio of different things.” source