In modern times much interest has been awakened in the Diatessaron; but all efforts to discover a copy in Syriac, which many believe to be its original language, have failed entirely; and no Greek copy, supposing that to be its language, has been found.

But there is in the Vatican Library an Arabic manuscript numbered XIV, which originally consisted of 125 leaves; but the 17th and 118th are missing. From its appearance, and the handwriting it is supposed to have been written in Egypt at some period from the twelfth to the fourteenth century, the latter date being the more probable. On the last page the copyist has written in Latin, "Here endeth, by the help of God, the Sacred Gospel, which Tatian collected out of the four Gospels, and which is commonly called the Diatessaron.

It was brought to the Vatican about A.D. 1719, Agostino Ciasca, one of the Guild of Writers to the Vatican wrote an essay upon it, which he published in Paris in 1883. In 1886 Ciasca showed this manuscript, among others, to Antonius Morcos, Visitor-Apostolic of the Catholic Copts, who said he had seen one like it in Egypt, and could obtain it for him.In August 1886 the promised manuscript arrived at Rome as a present to the Borgian Museum from its owner, Halim Dos Gali. It is evidently a copy of the same work as manuscript XIV, though it contains some important differences of detail. A note at each end plainly asserts that it is Tatian's Diatessaron.

This work Ciasca selected as the most suitable one for publication in honor of the Jubilee of the priesthood of Pope Leo XIII; and it was accordingly published in Rome in 1888 in the original Arabic, accompanied by a Latin translation, the working of the text being based on a careful comparison of the two manuscripts of the Vatican Library and the Borgian Museum. The present volume is an attempt to lay before the English reader a literal translation of the Diatessaron as published by Ciasca, with a short explanation of its history, contents, and bearing upon modern controversies.