8 Yet the Lord also has not left us to chance, since, in that He said, “The Son cannot of Himself do anything, but what He sees the Father doing,” He meant us to understand that the Father does, not some works which the Son may see, and the Son does other works after He has seen the Father doing; but that both the Father and Son do the very same works. For He goes on to say, “For what things soever He does, these also does the Son in like manner.” Not after the Father has done works, does the Son other works in like manner; but, “whatever He does, these also the Son does in like manner.”
If these the Son does which the Father does, then it is by the Son that the Father does: if by the Son the Father does what He does, then the Father does not some, the Son others; but the works of the Father and of the Son are the same works. And how does the Son also the same? Both “the same,” and “in like manner.” In case you should think them the same, but in a different manner, the “same,” says He, and “in like manner.” And how could they be the same and not in like manner?
Take an example, which I presume is not too big for you: when we write letters they are first formed by our heart, then by our hand. Certainly: why otherwise have you all agreed, but because you perceived it to be so? It is as I have said, it is manifest to us all. The letters are made first by our heart, then by our body; the hand serves, the heart commands; both the heart and the hand make the same letters. Do you think the heart does some letters, the hand some others? The same indeed does the hand, but not in like manner: our heart forms them intelligibly, but our hand visibly.
See how the same things are made, but not in like manner. Hence it was not enough for the Lord to say, “What things soever the Father does, these also the Son does;” He must add, “and in like manner.” For what if you should understand this just as you understand whatever your heart does, this also your hand does, but in a different manner? Here, however, he added, “These also the Son does in like manner.” If He both does these, and in like manner does, then awake; let the Jew be crushed, let the Christian believe, let the heretic be convinced: The Son is equal to the Father.
Source: Tractates on the Gospel of John (New Advent)