On The Holy Trinity by St. Augustine
Chapter 1.--God is Above the Mind.
1. Desiring to exercise the reader in the things that are made, in order that he may know Him by whom they are made, we have now advanced so far as to His image, which is man, in that wherein he excels the other animals, i.e. in reason or intelligence, and whatever else can be said of the rational or intellectual soul that pertains to what is called the mind. For by this name some Latin writers, after their own peculiar mode of speech, distinguish that which excels in man, and is not in the beast, from the soul, which is in the beast as well. If, then, we seek anything that is above this nature, and seek truly, it is God, -- namely, a nature not created, but creating. And whether this is the Trinity, it is now our business to demonstrate not only to believers, by authority of divine Scripture, but also to such as understand, by some kind of reason, if we can. And why I say, if we can, the thing itself will show better when we have begun to argue about it in our inquiry.