The Three Witnesses

Sane falli te nolo in Epistola Ioannis apostoli, ubi ait: Tres sunt testes; spiritus, et aqua, et sanguis; et tres unum sunt. Ne forte dicas spiritum et aquam et sanguinem diversas esse substantias, et tamen dictum esse: tres unum sunt; propter hoc admonui ne fallaris. Haec enim sacramenta sunt, in quibus non quid sint, sed quid ostendant semper attenditur: quoniam signa sunt rerum, aliud existentia, et aliud significantia. Si ergo illa quae his significantur, intellegantur, ipsa inveniuntur unius esse substantiae; tamquam si dicamus: Petra et aqua unum sunt, volentes per petram significare Christum; per aquam, Spiritum Sanctum: quis dubitat petram et aquam diversas esse naturas? Sed quia Christus et Spiritus Sanctus unius sunt eiusdemque naturae; ideo cum dicitur: Petra et aqua unum sunt; ex ea parte recte accipi potest, qua istae duae res quarum est diversa natura, aliarum quoque signa sunt rerum quarum est una natura. Tria itaque novimus de corpore Domini exisse, cum penderet in ligno: primo, spiritum; unde scriptum est: Et inclinato capite tradidit spiritum; deinde, quando latus eius lancea perforatum est, sanguinem et aquam. Quae tria si per se ipsa intueamur, diversas habent singula quaeque substantias; ac per hoc non sunt unum. Si vero ea, quae his significata sunt, velimus inquirere, non absurde occurrit ipsa Trinitas, qui unus, solus, verus, summus est Deus, Pater et Filius et Spiritus Sanctus, de quibus verissime dici potuit: Tres sunt testes, et tres unum sunt; ut nomine spiritus significatum accipiamus Deum Patrem: de ipso quippe adorando loquebatur Dominus, ubi ait: Spiritus est Deus. Nomine autem sanguinis, Filium; quia: Verbum caro factum est. Et nomine aquae Spiritum Sanctum: cum enim de aqua loqueretur Iesus, quam daturus erat sitientibus, ait evangelista: Hoc autem dixit de Spiritu, quem accepturi erant credentes in eum. Testes vero esse Patrem et Filium et Spiritum Sanctum, quis Evangelio credit, et dubitat, dicente Filio: Ego sum qui testimonium perhibeo de me: et testimonium perhibet de me, qui misit me, Pater? Ubi etsi non est commemoratus Spiritus Sanctus, non tamen intellegitur separatus. Sed nec de ipso alibi tacuit, eumque testem satis aperteque monstravit. Nam cum illum promitteret, ait: Ipse testimonium perhibebit de me. Hi sunt tres testes: et tres unum sunt, quia unius substantiae sunt. Quod autem signa quibus significati sunt, de corpore Domini exierunt, figuraverunt Ecclesiam praedicantem Trinitatis unam eamdemque naturam: quoniam hi tres qui trino modo significati sunt, unum sunt; Ecclesia vero eos praedicans, corpus est Christi. Si ergo tres res quibus significati sunt, ex corpore Domini exierunt: sicut ex corpore Domini sonuit, ut baptizarentur gentes in nomine Patris et Filii et Spiritus Sancti. In nomine; non: In nominibus; hi enim tres unum sunt, et hi tres unus est Deus. Si quo autem alio modo tanti sacramenti ista profunditas, quae in Epistola Ioannis legitur, exponi et intellegi potest secundum catholicam fidem, quae nec confundit nec separat Trinitatem, nec abnuit tres personas, nec diversas credit esse substantias, nulla ratione respuendum est. Quod enim ad exercendas mentes fidelium in Scripturis sanctis obscure ponitur, gratulandum est, si multis modis, non tamen insipienter exponitur. Sanctus Augustinus Hipponensi, Contra Maximinum Episcopum Arianorum, Lib II. Cap XXII Source: Migne PL 42 794-795

I would certainly not want you to err in the letter of John the Apostle, where he says, 'There are three witnesses: the spirit, and the water, and the blood; and the three are one.' 1 Lest perhaps you say that the spirit and the water and the blood are different substances, and yet it is said, 'the three are one' on which account I have warned you not to err. For these are mystical expressions, in which not what they are but what they are signs of should always be considered, because they are signs of things, and one thing is the essence and another the signification. If therefore the things signified are understood, we find them to be of one substance, as if we might say, 'The rock and the water are one,' meaning by the rock, Christ and by the water, the Holy Spirit, and who doubts that rock and water are different substances? But because Christ and the Holy Spirit are of one and the same nature, therefore when it is said that the rock and the water are one, this can be rightly be grasped, that these two things with different natures are yet signs of other things with one nature. Three things then we know to have issued from the Body of the Lord when He hung on the cross: first, the spirit, of which it is written, 'And He bowed His head and gave up the spirit' 2 ; then, when His side was pierced by the spear, 'blood and water.' 3 Which three things if we consider them as they are in themselves, each have their own substance, by which they are not one. If, however, we wish to enquire into the things they signify, there not unreasonably occurs to us the Trinity itself, which is the One, Only, True, Supreme God, Father and Son and Holy Spirit, of whom it can most truly be said, 'There are Three Witnesses,' and 'the Three are One,' so that by the name Spirit we should understand God the Father to be signified; as indeed it was concerning the worshiping of Him that the Lord was speaking when He said, 'God is a Spirit,' 4 and by the term, blood, the Son, because 'the Word was made flesh,' 5 and by the term water, the Holy Spirit, for when Jesus spoke of the water which He would give to those who thirst, the Evangelist says, 'But this He said about the Spirit which they that believed in Him were to receive.' 6 Moreover, that the Father, Son, and Holy Spirit are witnesses, who that believes the Gospel can doubt, when the Son says, 'I am one who bears witness to myself; and the Father who sent me, He bears witness to me.' ? 7 Where, even if the Holy Spirit is not mentioned, yet He is not to be thought separated from them. For concerning Him He was not silent elsewhere, and that He too is a witness has been sufficiently and openly shown. For in promising Him He said, 'He shall bear witness to me.' 8 These are the 'Three Witnesses,' and 'the Three are One', because there are of one substance. And because the signs by which they were signified issued from the Body of the Lord, they were a figure of the Church preaching the one and same nature of the Trinity, since these Three in threefold manner signified are One, but the Church that preaches them is the Body of Christ. If then the three things by which they are signified issued from the Body of the Lord, likewise from the Body of the Lord came the voice telling them to baptize the peoples 'In the Name of the Father and of the Son and of the Holy Spirit.' 9 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 the letter of John can be expounded and understood in accordance with the Catholic faith, which neither confounds nor divides the Trinity, nor denies three persons, nor believes in diverse substances, it must on no account be rejected. For that which exercises the minds of the faithful in things expressed obscurely in Holy Scripture, must be welcomed, even if in many ways, but not unwisely, it is explained. Saint Augustine of Hippo, from Against Maximinus Bishop of The Arians, Book 2, Chap 22 1 1 Jn 5.8 2 Jn 19.30 3 Jn 19.34 4 Jn 4.24 5 Jn 1.14 6 Jn 7.39 7 Jn 8.18 8 Jn 15.26 9 Mt 28.19