Isaac Iudaeus (aka Isaac the Jew) was a Jew who converted to Christianity and flourished around the time of Pope Damasus (Damasus, bishop of Rome), specifically AD 384, according to the editor of the Corpus Christianorum Series Latina, who is identified as "A. Hoste," probably Dom Anselm Hoste (CCSL, Vol. 9, p. 333). There is a tractate, known as "Fides Isatis ex Iudeao" or "Fide Isacis" (Faith of Isaac the Jew), which Hoste acknowledges to be genuine.
On the other hand, there is a work sometimes ascribed to this same Isaac the Jew, known as the "Expositio Fidei Catholicae" (Exposition of the Catholic Faith), but which the Clavis Patrum Latinorum (n. 190) is reluctant to acknowledge as authentic and multiple scholars agree. The work is preserved in a single 8th century manuscript.
The critically restored text in CCSL, vol. 9, is as follows:
EXPOSITIO FIDEI CATHOLICAE
Credimus unum deum secundum scripturam esse credendum, non sicut Iudaei aut haeretici, solitarium, sed in mysterio trinitatis, id est patrem et filium et spiritum sanctum, tres personas, non tamen tres deos.
Personas autem sic dicimus, ut non diuinitatem haeretico sensu membris, sicut hominem, conponamus, quia diuinitas quae est incorporalis tam inmensa est, tam inextimabilis, ut intra se omnia contineat, ipsa autem circumscribi non possit, sed ut patrem et filium et spiritum sanctum unum et indiuisum esse ita in diuinitate ac uirtute <credamus>, ut tres in personis, id est ut patrem credamus non esse filium, filium uero credamus non esse patrem, spiritum autem sanctum nec patrem esse nec filium; quia pater est ingenitus, filius uero sine initio genitus a patre est, spiritus autem santus processit a patre et accipit de filio, sicut euangelista testatur, quia scriptum est: Tres sunt, qui dicunt testimonium in caelo: pater, uerbum et spiritus, et haec tria unum sunt in Christo Iesu. Non tamen dixit: unus est in Christo Iesu.
Et in euangelio dicit: Ite, baptizate gentes in nomine patris et filii et spiritus sancti. Et denuo ipse dominus dicit: Ego et pater unum sumus. Et in psalmis legimus: Dicit dominus domino meo: Sede a dextris meis. Et in euangelio Iohannis sic dicit: In principio erat uerbum, et uerbum erat apud deum, et deus erat uerbum.
Deum ergo dicendum uerbum, id est filium qui est apud patrem. Deum bis nominando deum patrem et filium designauit personas. Et in Genesi deus pater ad deum filium dicit: Faciamus hominem ad imaginem et similitudinem nostram. Et denuo: Fecit deus hominem ad imaginem dei.
Igitur ter deum dicendo non tres deos dixit, sed unum deum in tribus personis demonstrauit, nullum sane, sicut Arrius, altero maiorem. Quia autem tempore aut mensura aut honore unus quisque alio maior <non> est, ideo nos credimus, filium dei sine tempore a patre genitum. Quomodo potest minor esse tempore, qui ante tempore est? Aut quomodo mensura minor creditur, qui inmensus et inextimabilis est? et infinitus est? ac honore minor est, cum sit filius dei et deus? Vnum enim dei nomen est.
Quando autem sit filius a patre genitus, aut ubi, aut quomodo, non licet dici, neque amplius scrutari. Quando autem dicendo tempus designas, ubi requirendo locum significas, quomodo scrutando mensuram uideris exprimere. Et haec tria in domino non cadunt, quia est inextimabilis, inmensus, infinitus, et quia locum non capit, quem mens nostra, quae modo concluditur, <inuestigare possit>.
Inuestigare nemo potens factorem et dominum suum. Sicut ergo in hac trinitate una et inseparabilis est substantia atque diuinitas, ita et una est omnipotentia, non tres. Omnipotentia enim in eo dicitur, quod potentia et uirtute sua deus ex nihilo fecit uniuersa, id est caelestia et terrestria, carnalia et spiritalia, lucem atque tenebras, uisibilia et inuisibilia, angelos et animas et quidquid praeter deum mens humana crediderit.
Et haec bona per filium facta sunt, sanctificata spiritu sancto, quem paracletum appellamus, qui super apostolis...
Here is my unprofessional translation of the Latin text (I would welcome a more professional translation):
Exposition of the Catholic Faith
We believe that one God, according to Scripture, is to be believed—not, as the Jews or heretics, solitary, but in the mystery of the Trinity, that is, the Father and the Son and the Holy Spirit, three persons, yet not three gods.
But we speak of persons in this way: not so that we may compose the divinity, in a heretical sense, with limbs, as a human being, because the divinity, which is incorporeal, is so immense, so inestimable, that it contains all things within itself, but itself cannot be circumscribed; but so that we may believe the Father and the Son and the Holy Spirit to be one and undivided in divinity and power, while three in persons—that is, so that we believe the Father not to be the Son, and we believe the Son not to be the Father, and the Holy Spirit to be neither the Father nor the Son. For the Father is unbegotten, but the Son was begotten by the Father without beginning, and the Holy Spirit proceeded from the Father and receives from the Son, as the evangelist testifies, because it is written: “There are three who speak testimony in heaven: the Father, the Word, and the Spirit, and these three are one in Christ Jesus.” Yet he did not say: “This is [TF note: i.e., in the singular] one in Christ Jesus.”
And in the Gospel he says: “Go, baptize the nations in the name of the Father and of the Son and of the Holy Spirit.” And again the Lord himself says: “I and the Father are one.” And in the Psalms we read: “The Lord said to my Lord: Sit at my right hand.” And in the Gospel of John he speaks thus: “In the beginning was the Word, and the Word was with God, and God was the Word.”
Therefore the Word is to be called God, that is, the Son who is with the Father. By naming God twice, he designated the persons, God the Father and the Son. And in Genesis God the Father says to God the Son: “Let us make man according to our image and likeness.” And again: “God made man according to the image of God.”
Therefore, by saying “God” three times, he did not speak of three gods, but showed one God in three persons—certainly no one, as Arius, greater than another. But because each one is not greater than another in time or measure or honor, therefore we believe the Son of God to have been begotten by the Father without time. How can he be lesser in time, who is before time? Or how is he believed to be lesser by measure, who is immeasurable and inestimable? And is he infinite? And is he lesser in honor, since he is the Son of God and God? For there is one name of God.
But when the Son was begotten by the Father, or where, or how, it is not permitted to say, nor to investigate further. For when, by saying “when,” you indicate time; by asking “where,” you signify place; by investigating “how,” you seem to express measure. And these three things do not fall upon the Lord, because he is inestimable, immeasurable, infinite, and because he does not take up place—whom our mind, which is now enclosed, is not able to investigate [TF note: the scholarly conjecture "investigare possit" suggests we "can investigate" it, but see the next line of the text].
No one is able to investigate his Maker and Lord. Therefore, just as in this Trinity there is one and inseparable substance and divinity, so also there is one omnipotence, not three. For omnipotence is spoken of in this, that God, by his own power and strength, made all things out of nothing, that is, heavenly and earthly things, fleshly and spiritual things, light and darkness, visible and invisible things, angels and souls, and whatever the human mind might believe besides God.
And these good things were made through the Son, sanctified by the Holy Spirit, whom we call the Paraclete, who upon the apostles...
A few observations about the form of the Johannine Comma as found here. First, the text of the comma is: "Tres sunt, qui dicunt testimonium in caelo: pater, uerbum et spiritus, et haec tria unum sunt in Christo Jesu."
We cannot tell from this quotation whether this comes before or after the earthly witnesses for Ps-Isaac. The text, such as is present, differs only slightly from Priscillian's text: "tria sunt quae testimonium dicunt in caelo: pater, uerbum et spiritus et haec tria unum sunt in Christo Jesu." (see more complete discussion of Priscillian here)
Thus, like Priscillian's text, "in Christ Jesus" is present and the phrase "these three are one in Christ Jesus" uses neuter forms of "these" and "three". Also like Priscillian's text, the word "holy" does not accompany "spirit". Additionally, like Priscillian's text, the concept of testifying is expressed in terms of uttering testimony, although the order of the words is swapped. Notably, perhaps, "three" and "which" are masculine in the first instance, in contrast to Priscillian.
Ps-Isaac does not explicitly identify John as the author, but does ascribe the phrase to the "evangelist." By contrast, Priscillian says John said it, but does not specify whether it is John the Evangelist.
Among scholarly references to the work, we have:
- "32. Dubie Isaac Iudaeus (fl. c. 384), Expositio fidei catholicae; CPL 190; PF/EF." (Gyug, R. F. (2017). Ritual, Text and Law: Studies in Medieval Canon Law and Liturgy Presented to Roger E. Reynolds. United Kingdom: Taylor & Francis. link)
- "18] f. 74r-v, <Expositio fidei catholica, mutila alla fine> (<inter dubia> di Isaac = Ambrosiaster ? CPL 190, da questo solo codice; <in Africa saec. V-VI composita >, F. Stegmüller, Repertorium Biblicum Medii Aevi, VI, ..." (Italia medioevale e umanistica. (1989). Italy: Editrice Antenore.. link)
- "The other critic is the author of an Expositio fidei catholicae[52], a text which is related to the Fides of Isaac the Jew.[53] Here the phrase clearly occurs as a variant of the Comma Johannaeum. The Expositio reads: Tres sunt qui dicunt testimonium in caelo: pater, uerbum et spiritus, at haec tria unum sunt in Christo Jesu. Then follows the criticism: Non tamen dixit: 'unus est in Christo Iesu.'" (Bijdragen tijdschrift voor filosofie en theologie. (1991). Netherlands: Redactie Bijdragen. p. 362)
There is a problem of trying to date this work. Clare K. Rothschild sums up the state of the scholarship this way:
In short, there are some scholars who date the text (as distinct from the manuscript) to the fifth or sixth century, others that date it as early as the second half of the fourth century. The dating of the text is, unhelpfully for us, tied to the emergence of the Johannine Comma. There may be other theological issues that could assist dating of the work. For example, while the late 5th century work of Victor (discussed here) describes the procession of the Spirit as being from the Father, but makes no mention of the Son in this context, the author of the present work suggests that the Spirit, in addition to proceeding from the father, "et accipit de filio" (and receives from the Son).
From my standpoint, this suggests the possibility of later doctrinal development, although it is hard to be sure. Given that the manuscript itself is dated to the 8th century, that provides an outer bound on the date of composition. If we were to take a late 7th or even 8th century date as the date of composition, the reference to "heretics" could be a reference to the Unitarianism of the Muslims of those centuries.
I sought in vain for any researcher on the historical development of the Filioque providing any other historical example of "receives from the Son" in any language. If anyone knows, I would love to update this discussion with such a detail.
I certainly concur with Karl Künstle that this seems very unlikely to be the work of the same Isaac whose "Faith of Isaac the Jew" is known to us. Given that the comma is the first text that the present author cites in this relatively short work, it is unlikely that the same author would not have mentioned the comma in his longer work. So, it seems safe to say that the author is simply unknown, although he stands against both Unitarian and Arian views.
Ultimately, this text stands as another witnesses to a form of the Johannine Comma similar to that of Priscillian from the late 4th century, arguably the earliest discernable form of the interpolation.
