The oldest witness to the Diatessaron in the West is a sixth- century Latin manuscript of the New Testament. Its gospels, however, are in the form of a harmony. Known as Codex Fuldensis, it was copied at the order of bishop Victor of Capua. Writing on 2 May 546, Victor concluded a Preface to the manuscript, which begins as follows:
By chance, into my hands fell one Gospel having been composed from the four. And as absent a title and I could not find the name of the author. By carefully inquiring which deeds or sayings of our Lord and Saviour with the readings from Separate Gospels into the order which themselves were being seen to follow with not the least effort of (this) work, he will have rendered. I have discovered Ammonius a certain Alexandrian, who of the tables and likewise of the Gospel is considered the author.
Who using the Matthew’s Gospel and selected parts of the other three, to have joined and woven them thus into a unified continuous Gospel. Like bishop Eusebius, writing to a certain Carpianus in the preface of his book in which the tables of the said Gospel he has published, his following of the aforementioned man’s devotion shows in this way: "Ammonius, this Alexandrian, I consider how much exerting of effort and energy (has) bequeathed us, the Unified Gospel, taken from the Quartet."
From each account of his I have learned that Tatianus, [a learned man and clear orator of that time], has been able to assemble a Unified Gospel from the Quartet, to which he gave the title Diapente, (Through Five). [This (man) became the disciple of Saint Justin, the philosopher and martyr, while he lived with him. Whose passing away to the Lord, with the victory of the Master’s martyrdom, (caused Tatian’s) abandoning the holy teaching also (as he was) exalted (to) haughty doctrine, (and) into the Encratites’ fallen heresy with Marcionites, rather (to take) the clasp of the error than Justin’s, Christ’s philosopher’s truth to his life. A pernicious asserting he has cultivated among other things, that marriage and debauchery (are) to be subject to equal condemnation. But also, to the Apostolic sayings, common scribe’s correction, or how truly I may say, corruption, he is said, to have inflicted]. But also because faithless men’s confession to Christ, our God’s power of working or by exertion (it) often triumphs over the glory of the truth for also demons were confessing Christ and the sons of Sceva, who in the Acts of the Apostles, were exorcising demons in the name of Jesus, of whom Paul would preach. Tatian too, although involved in profane errors, nevertheless, placed before savants an example which is not useless, arranged this gospel — as it seems to me — with skillful composition. Tatian too, although involved in profane errors, nevertheless, still adhering to the side of the blessed Justin, thanks to the latter's erudition. For the following reason I think that the edition of the above mentioned volume was not by Ammonius but of the aforementioned’s edition to be the book, where Ammonius is brought to Matthew’s account with the remaining evangelists separate accounts to be attached: "here indeed the beginnings of Saint Luke are taken, although the greatest part (is) from the Gospel of Saint Matthew, (with) the remaining three he may have continued the sayings without a break, as justly doubt could be Ammonius’ or Tatian’s composition with his works ought to be valued the same. Nevertheless, take what you will, if now as a leader of heretics, this composition’s author, Tatian has emerged, the words of my Lord, I recognising, willingly embrace: if it might have been his own interpretation, far, I would cast it aside. Now also ‘Against the Nations’ and (other) splendid books he is reported to have had published.
Although Victor's Latin is awkward and at points opaque, this preface is important for what it tells us about knowledge of the Diatessaron in the West, and about the document he ordered copied.
It is apparent that the Diatessaron was not commonly known in the West at this time; otherwise, Victor would have immediately recognized what had come into his hands. Victor's research led him to Eusebius who, as we already know, mentions two Diatessarons: Tatian's and Ammonius'. The basis upon which Victor decided the issue of authorship — namely, that Ammonius' Diatessaron was built around Matthew, but the work in question commences with Luke — probably indicates that the manuscript which came into his hands began with a passage from Luke. Codex Fuldensis also begins with Luke 1.1-4, followed by John 1.1-4, followed by Luke 1.5-15. Victor's remark suggests that Codex Fuldensis' incipit agrees with its archetype's incipit? Although Victor obviously has no love for Tatian the heretic, the harmony before him evoked respect: God can use even evil men for good purposes, and Victor regarded the harmony as a "skillful composition." Victor's suggestion that Tatian composed the harmony while still under the watchful eye of the orthodox Justin is probably more a pious wish than a historical circumstance. Victor's difficulty in deciding whether Ammonius of Alexandria or Tatian was the author of the document is symptomatic of other ancient writers who also confuse the two. JC Zahn (1814) decided the issue in favour of Tatian with a logic which remains definitive, but uncertainty is found in the literature as late as the 1920s. Victor's description of the document as an "[in] unum ex quattuor" is intelligible, for this is the superscription borne by some Latin harmonies in the West. On the other hand, Victor's title for the work, "dia-pente" (not "dia-tessaron"), has puzzled scholars. Various explanations have been proposed. Some have interpreted it as a simple error;43 others have seen in it Victor's recognition that Tatian incorporated a "fifth source" into the Diatessaron, namely one of the lost Judaic-Christian gospels (scholars usually suggest the Gospel according to the Hebrews [modern scholars' Gospel according to the Ebionites] as the most likely candidate); it has even been suggested that Victor's copy of Eusebius' H.E. was defective, and read "diapente"; it has also been interpreted in terms of musicology, in which "diapente" references the chord or interval of the fifth. This musical explanation of Victor's "Diapente" warrants examination, for it has attracted proponents for over three hundred years. It originated in 1614 with Isaac Casaubon (1559 - 1614); an independent Huguenot scholar, friend of Theodore Beza in Geneva, who corresponded with Scaliger and Daniel Heinsius in Leiden) who suggested that
In the Preface of Victor of Capua, which is found in the seventh tome of the Bibliotheca Patrum recently published in Paris, page 25, we read as follows: Tatian composed one Gospel out of the four, and he entitled it "Dia pente." It seems that we should write "Dia panton," which agrees with [what we find in] Eusebius. We know otherwise that "Dia pente" was [used as] the name of a harmony among musicians, just like Dia tessaron & Dia pason: also Latins like Vitruvius kept to these [Greek] terms.
Marcus Vitruvius Pollio, a first century BCE writer on architecture, uses the term diapason (διά πασων) to reference the musical octave; dia pente (διὰ πέντε) to reference the musical fifth (made up of four steps: C to G in current mucial notation); and dia tessaron (δια τεσσάρων) to reference the interval of a fourth (made up of three steps: C to F). According to those who propound this view, Tatian, thinking of the four gospels as equivalent to the "harmony" of the fourth, named his gospel harmony δια τεσσάρων. Citing Pythagorean musical terminology, Paul de Lagarde embraced this explanation and thought it explained both Tatian's title and Victor's title. Th. Zahn dismissed the idea, observing that the theory deserved no further attention. A. Hjelt reported it, but reserved his opinion. The most recent proponent is Franco Bolgiani. He suggests that while Tatian thought in terms of terminology (where a harmony of the four gospels would be called a δια τεσσάρων. Victor calculated differently: for Victor, a work composed from four gospels should be referenced by four steps (notes C to D [step 1], D to E [step 2], E to F [step 3], and F to G [step 4]), that is, the diapente (the fifth, C to G). It is incontestable that the terms diatessaron and diapente were used in music; the theory that these musical ideas inspired the titles handed down to us must, however, remain a conjecture, for no ancient author explains the title in terms of musical theory. [Petersen, Diatessaron p. 47 - 51]
