17 Let us see then, if haply we cannot find something in the creature whereby we may prove that some three things are exhibited separately whose operation is yet inseparable. But whither shall we go? To the heaven, to dispute of the sun and moon and stars? To the earth, to dispute of shrubs, and trees, and animals which fill the earth? Or of the heaven and the earth itself, which contain all the things that are in heaven and earth? How long, O man, will you roam over the creation?
Return unto yourself, see, consider, examine your own self. You are searching among the creatures for some three things which are separately exhibited, whose operation is yet inseparable; if then you are searching for this among the creatures, search for it first in your own self. For you are not other than a creature. It is a resemblance you are searching for. Would you search for it among the cattle? For of God it was you were speaking, when you were in search for this resemblance.
You were speaking of the Trinity of Majesty ineffable, and because you failed in contemplating the Divine Nature, and with becoming humility confessed your infirmity, you came down to human nature; there then pursue your enquiry. Will you make your search among the cattle, in the sun, or the stars? What of these was made after the image and likeness of God? You may search in your own self for something more familiar to you, and more excellent than all these. For God made man after His own image and likeness.
Search then in your own self, if haply the image of the Trinity bear not some vestige of the Trinity. And what is this image? It is an image very different from its model; yet different as it is, it is an image and a likeness notwithstanding, not indeed in the same way as the Son is the Image, being the Same Which the Father is. For an image is in one sort in a son, and in another in a mirror. There is great difference between them. Your image in your son is your own self, for the son is by nature what you are.
In substance the same as you, in person other than you. Man then is not an image as the Only-begotten Son is, but made after a sort of image and likeness. Let him then search for something in himself, if so be he may find it, even for some three things which are exhibited separately, whose operation is yet inseparable. I will search, and do ye search with me. I will not search in you, but do ye search in yourselves, and I in myself. Let us search in concert, and in concert discuss our common nature and substance.
Source: Sermons on Selected Lessons of the New Testament (New Advent)