For whatever exists in God is the essence, or a person, or a notion. But the order of nature does not signify the essence, nor any of the persons, or notions. Therefore there is no order of nature in God.
 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

“_______________________
THIRD ARTICLE [I, Q. 42, Art. 3]
Whether in the Divine Persons There Exists an Order of Nature?
Objection 1: It would seem that among the divine persons there does not exist an order of nature. For whatever exists in God is the essence, or a person, or a notion. But the order of nature does not signify the essence, nor any of the persons, or notions. Therefore there is no order of nature in God. Obj. 2: Further, wherever order of nature exists, there one comes before another, at least, according to nature and intellect. But in the divine persons there exists neither priority nor posteriority, as declared by Athanasius.” source