From Select Treatises of St. Athanasius
Translated by Venerable John Henry Newman

And the same of He that hath seen Me, hath seen the Father, and I and the Father are One, for this the Son says, and not the Word, as they would have it, as is plain from the Gospel; for according to John when the Lord said, I and the Father are One, the Jews took up stones to stone Him. Jesus answered them, Many good works have I shewed you from My Father, for which of those works do ye stone Me? The Jews answered Him, saying, For a good work we stone Thee not, but for blasphemy, and because that Thou, being a man, makest Thyself God. Jesus answered them, Is it not written in your law, I said, Ye are gods? If He called them gods unto whom the Word of God came, and the Scriptures cannot be broken, say ye of him, whom the Father hath sanctified and sent into the world, Thou blasphemest, because I said, I am the Son of God? If I do not the works of My Father, believe Me not. But If I do, though ye believe not Me, believe the works, that ye may know and believe that the Father is in Me, and I in the Father [John x. 32-38.]. And yet, as far as the surface of the words intimated, He said neither "I am God," nor "I am Son of God," but I and the Father are One.The Jews, then, when they heard One, thought like Sabellius, that He said that He was the Father, but our Saviour shews their sin by this argument; "Though I said God, you should have remembered what is written, I said, Ye are gods." Then to clear up I and the Father are One, He has explained the Son's oneness with the Father in the words, Because I said, I am the Son of God. For if He did not say it in the letter , still He has explained as to the sense are One of the Son. For nothing is one with the Father, but what is from Him. What is That which is from Him but the Son? And therefore He adds, that ye may know that I am in the Father and the Father in Me. For, when expounding the One, He said that the union and the inseparability lay, not in This being That, with which It was One, but in His being in the Father and the Father in the Son. For thus He overthrows both Sabellius, in saying, not, I am "the Father," but, the Son of God; and Arius, in saying, are One.