The likeness of Christ to the Father is asserted on the authority of St. Paul, the prophets, and the Gospel, and especially in reliance upon the creation of man in God's image.
48. The Apostle saith that Christ is the image of the Father -- for he calls Him the image of the invisible God, the first-begotten of all creation. First-begotten, mark you, not first-created, in order that He may be believed to be both begotten, in virtue of His nature, and first in virtue of His eternity. In another place also the Apostle has declared that God made the Son |heir of all things, by Whom also He made the worlds, Who is the brightness of His glory, and the express image of His substance.| The Apostle calls Christ the image of the Father, and Arius says that He is unlike the Father. Why, then, is He called an image, if He hath no likeness? Men will not have their portraits unlike them, and Arius contends that the Father is unlike the Son, and would have it that the Father has begotten one unlike Himself, as though unable to generate His like.
49. The prophets say: |In Thy light we shall see light;| and again: |Wisdom is the brightness of everlasting light, and the spotless mirror of God's majesty, the image of His goodness.| See what great names are declared! |Brightness,| because in the Son the Father's glory shines clearly: |spotless mirror,| because the Father is seen in the Son: |image of goodness,| because it is not one body seen reflected in another, but the whole power [of the Godhead] in the Son. The word |image| teaches us that there is no difference; |expression,| that He is the counterpart of the Father's form; and |brightness| declares His eternity. The |image| in truth is not that of a bodily countenance, not one made up of colours, nor modelled in wax, but simply derived from God, coming out from the Father, drawn from the fountainhead.
50. By means of this image the Lord showed Philip the Father, saying, |Philip, he that sees Me, sees the Father also. How then dost thou say, Show us the Father? Believest thou not that I am in the Father, and the Father in Me?| Yes, he who looks upon the Son sees, in portrait, the Father. Mark what manner of portrait is spoken of. It is Truth, Righteousness, the Power of God: not dumb, for it is the Word; not insensible, for it is Wisdom; not vain and foolish, for it is Power; not soulless, for it is the Life; not dead, for it is the Resurrection. You see, then, that whilst an image is spoken of, the meaning is that it is the Father, Whose image the Son is, seeing that no one can be his own image.
51. More might I set down from the Son's testimony; howbeit, lest He perchance appear to have asserted Himself overmuch, let us enquire of the Father. For the Father said, |Let us make man in Our image and likeness.| The Father saith to the Son |in Our image and likeness,| and thou sayest that the Son of God is unlike the Father.
52. John saith, |Beloved, we are sons of God, and it doth not yet appear what we shall be: we know that if He be revealed, we shall be like Him.| O blind madness! O shameless obstinacy! We are men, and, so far as we may, we shall be in the likeness of God: dare we deny that the Son is like God?
53. Therefore the Father hath said: |Let us make man in Our image and likeness.| At the beginning of the universe itself, as I read, the Father and the Son existed, and I see one creation. I hear Him that speaketh. I acknowledge Him that doeth: but it is of one image, one likeness, that I read. This likeness belongs not to diversity but to unity. What, therefore, thou claimest for thyself, thou takest from the Son of God, seeing, indeed, that thou canst not be in the image of God, save by help of the image of God.