Of the Image of the Supreme Trinity, Which We Find in Some Sort in Human Nature Even in Its Present State
And we indeed recognize in ourselves the image of God, that is, of the supreme Trinity, an image which, though it be not equal to God, or rather, though it be very far removed from Him—being neither co-eternal, nor, to say all in a word, consubstantial with Him—is yet nearer to Him in nature than any other of His works, and is destined to be yet restored, that it may bear a still closer resemblance. For we both are, and know that we are, and delight in our being, and our knowledge of it.
Moreover, in these three things no true-seeming illusion disturbs us; for we do not come into contact with these by some bodily sense, as we perceive the things outside of us—colors, e.g., by seeing, sounds by hearing, smells by smelling, tastes by tasting, hard and soft objects by touching—of all which sensible objects it is the images resembling them, but not themselves which we perceive in the mind and hold in the memory, and which excite us to desire the objects. But, without any delusive representation of images or phantasms, I am most certain that I am, and that I know and delight in this.
In respect of these truths, I am not at all afraid of the arguments of the Academicians, who say, What if you are deceived? For if I am deceived, I am. For he who is not, cannot be deceived; and if I am deceived, by this same token I am. And since I am if I am deceived, how am I deceived in believing that I am? For it is certain that I am if I am deceived. Since, therefore, I, the person deceived, should be, even if I were deceived, certainly I am not deceived in this knowledge that I am.
And, consequently, neither am I deceived in knowing that I know. For, as I know that I am, so I know this also, that I know. And when I love these two things, I add to them a certain third thing, namely, my love, which is of equal moment. For neither am I deceived in this, that I love, since in those things which I love I am not deceived; though even if these were false, it would still be true that I loved false things. For how could I justly be blamed and prohibited from loving false things, if it were false that I loved them?
But, since they are true and real, who doubts that when they are loved, the love of them is itself true and real? Further, as there is no one who does not wish to be happy, so there is no one who does not wish to be. For how can he be happy, if he is nothing?
Source: City of God (New Advent)