The reader of these reflections of mine on the Trinity should bear in mind that my pen is on the watch against the sophistries of those who scorn the starting-point of faith and allow themselves to be deceived through an unseasonable and misguided love of reason. Some of them try to transfer what they have observed about bodily things to incorporeal and spiritual things, which they would measure by the standard of what they experience through the senses of the body or learn by natural human intelligence, lively application, and technical skill. There are others whose concept of God, such as it is, ascribes to Him the nature and moods of the human spirit, a mistake which ties their arguments about God to distorted and misleading rules of interpretation. Again, there is another type: people who, indeed, strive to climb above the created universe, so ineluctably subject to change, and raise their regard to the unchanging substance which is God. But, so top-heavy are they with the load of their mortality that what they do not know they wish to give the impression of knowing, and what they wish to know they cannot, and so they block their own road to genuine understanding by asserting too categorically their own presumptuous opinions and then, rather than change a misconceived opinion they have defended, they prefer to leave it uncorrected.
Indeed, this disease is common to all three types I have mentioned – to those who conceive of God in bodily terms, those who do so in terms of created spirit, such as soul, and those who think of Him neither as body nor as created spirit, but still have false ideas about Him, ideas which are all the further from the truth, in that they have no place either in the world of body or in that of derived and created spirit or in the Creator Himself. Thus, whoever thinks that God is dazzling white, for example, or fiery red, is mistaken, yet these are realities of the bodily world. Or, whoever thinks that God forgets things one moment and remembers them the next, or anything like that, is certainly quite wrong, and yet these are realities of the mental world. But, those who suppose that God is of such power that He actually begets Himself are, if anything, even more wrong, since not only is God not like that, but neither is anything in the world of body or spirit. There is absolutely no thing whatsoever that brings itself into existence.
From: The Trinity by Augustine; translated from the Latin by Edmund Hill; The Works of Saint Augustine: A Translation for the 21st Century series (Brooklyn: New City Press, 1991), pp. 65-66. (The Trinity 1.1.1)