“For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one.” – 1 John 5:7
When the text says, and these three are one, it is not [εἰς unus] one and the same person; but [ἓν unum] one and the same thing in effect [or, purpose], i.e. one and the same testimony. Even if the Comma Johanneum is genuine, which I do not grant, the phrase ἓν εἰσι (are one) could not be proved in this text, to mean anything more than agreeing in one and the same testimony. Beza himself understood the oneness here spoken of, to be only oneness in testimony. Consider the words of Christ’s prayer for his disciples, “that they may be one, ὦσιν ἓν, as we are.” Are we to then conclude, that the disciples are one individual being? I do not cite this text to say that if it does not mean unity of being there, then it can not mean unity of being here. That would be a word fallacy (illegitimate totality transfer). However, what I am saying is that it is apparent that a unity of concord (agreement) is an entirely different thing from a unity of being. And since the Greek expression nowhere appears to indicate a unity of essence, this unity must be proved by the context or by some other argument. The only type of union that can be inferred from the text, is one of testimony: “there are three that bear testimony, μαρτυροῦντες,” v. 7. There is no hint of any unity of metaphysical nature or essence in the surrounding context, but the text deals wholly with testimony, viz. “that Jesus is the Son of God,” v. 5. It is therefore completely unwarranted to use the Comma Johanneum, regardless of its authenticity, as justification for the notion that the three persons are one individual being.
The above is the combination of the insightful thoughts of Clarke, Pierce, and Alexander Asciutto on the spurious text of the Johannine comma. See Alexander Asciutto’s website here.