Contra Maximinum, lib. ii. c. 22 §. 3.

1 Joann. v. 7, 8. Tres sunt testes; spiritus, et aqua, et sanguis; et tres unum sunt.1 The clause of “the Three Heavenly Witnesses,” v. 7, appears to be wholly unknown to St. Augustin: a circumstance left unexplained by Mill, who asserts that copies which had the clause “abounded in Africa” in the interval between St. Cyprian and the close of the fifth century.

I would not have thee mistake that place in the epistle of John the apostle where he saith, “There are three witnesses: the Spirit, and the water, and the blood: and the three are one.” Lest haply thou say that the Spirit and the water and the blood are diverse substances, and yet it is said, “the three are one:” for this cause I have admonished thee, that thou mistake not the matter. For these are mystical expressions, 2 Sacramenta. in which the point always to be considered is, not what the actual things are, but what they denote as signs: since they are signs of things, and what they are in their essence is one thing, what they are in their signification another. If then we understand the things signified, we do find these things to be of one substance. Thus, if we should say, the rock and the water are one, meaning by the Rock, Christ; by the water, the Holy Ghost: who doubts that rock and water are two different substances? yet because Christ and the Holy Spirit are of one and the same nature, therefore when one says, the rock and the water are one, this can be rightly taken in this behalf, that these two things of which the nature is diverse, are signs of other things of which the nature is one. Three things then we know to have issued from the Body of the Lord when He hung upon the tree: first, the spirit: of which it is written, “And He bowed the head and gave up the spirit:” 3 John xix. 30, 34. then, as His side was pierced by the spear, “blood and water.” Which three things if we look at as they are in themselves, they are in substance several and distinct, and therefore they are not one. But if we will inquire into the things signified by these, there not unreasonably comes into our thoughts the Trinity itself, which is the One, Only, True, Supreme God, Father and Son and Holy Ghost, of whom it could most truly be said, “There are Three Witnesses, and the Three are One:” so that by the term Spirit we should understand God the Father to be signified; as indeed it was concerning the worshipping of Him that the Lord was speaking, when He said, “God is a Spirit:”4 John iv. 24. by the term, blood, the Son; because “the Word was made flesh:”5 John i. 14. and by the term water, the Holy Ghost; as, when Jesus spake of the water which He would give to them that thirst, the evangelist saith, “But this said He of the Spirit which they that believed on Him were to receive.”6 John vii. 39. Moreover, that the Father, Son, and Holy Ghost are “Witnesses,” who that believes the Gospel can doubt, when the Son saith, “I am one that bear witness of myself, and the Father that sent me, He beareth witness of me.”7 John viii. 18. Where, though the Holy Ghost is not men tioned, yet He is not to be thought separated from them. Howbeit neither concerning the Spirit hath He kept silence elsewhere, and that He too is a witness hath been sufficiently and openly shown. For in promising Him He said, “He shall bear witness of me.”8 John xv. 26. These are the “Three Witnesses,” and the Three are One, because of one substance. But whereas, the signs by which they were signified came forth from the Body of the Lord, herein they figured the Church preaching the Trinity, that it hath one and the same nature: since these Three in threefold manner signified are One, and the Church that preacheth them is the Body of Christ. In this manner then the three things by which they are signified came out from the Body of the Lord: like as from the Body of the Lord sounded forth the command to “baptize the nations in the Name of the Father and of the Son and of the Holy Ghost.”9 Matt. xxviii. 19. “In the name:” not, In the names: for “these Three are One,” and One God is these Three. And if in any other way this depth of mystery which we read in John’s epistle can be expounded and understood agreeably with the Catholic faith, which neither confounds nor divides the Trinity, neither believes the substances diverse nor denies that the persons are three, it is on no account to be rejected. For whenever in Holy Scriptures in order to exercise the minds of the faithful any thing is put darkly, it is to be joyfully welcomed if it can be in many ways but not unwisely expounded.