We indeed recognize in ourselves the image of God, that is, of the supreme Trinity. For we 1. both are, and 2. know that we are, and 3. delight in our being, and our knowledge of it. Moreover, in these three things no true-seeming illusion disturbs us.
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.
St. Augustine – Of the Image of the Supreme Trinity in Human Nature. The City of God XI, 26