[…] In what does the greatness of man consist, according to the doctrine of the Church?
Not in his likeness to the created world, but in his being in the image of the nature of the Creator.
[…] What is it then which we understand concerning these matters?
In saying that “God created man” the text indicates, by the indefinite character of the term, all mankind.
For was not Adam here named together with the creation, as the history tells us in what follows?
Yet the name given to the man created is not the particular, but the general name.
Thus we are led by the employment of the general name of our nature to some such view as this—that in the Divine foreknowledge and power all humanity is included in the first creation.
For it is fitting for God not to regard any of the things made by Him as indeterminate, but that each existing thing should have some limit and measure prescribed by the wisdom of its Maker.
Any particular man is limited by his bodily dimensions, and the peculiar size which is conjoined with the superficies of his body is the measure of his separate existence.
So also I think that the entire plenitude of humanity was included by the God of all, by His power of foreknowledge, as it were in one body, and that this is what the text teaches us which says, “God created man, in the image of God created He him.”
For the image is not in part of our nature, nor is the grace in any one of the things found in that nature, but this power extends equally to all the race.
And a sign of this is that mind is implanted alike in all: for all have the power of understanding and deliberating, and of all else whereby the Divine nature finds its image in that which was made according to it.
The man that was manifested at the first creation of the world, and he that shall be after the consummation of all, are alike: they equally bear in themselves the Divine image.
For this reason the whole race was spoken of as one man, namely, that to God’s power nothing is either past or future, but even that which we expect is comprehended, equally with what is at present existing, by the all-sustaining energy.
Our whole nature, then, extending from the first to the last, is, so to say, one image of Him Who Is.
Gregory of Nyssa (c 335 – after 394): On the Making of Man, 16, 1,2,16-18 (slightly adapted).