Eusebius' work has been published by Gaisford: Eusebii Pamph. contra Hieroclem et Marcellum libri, Oxon. 1852; and also in various editions of the works of Philostratus. Migne, Opera IV. 795 sq., reprints it from Olearius' edition of Philostratus' works (Lips. 1709).
Against Porphyry (kata Porphurion). Porphyry, the celebrated Neo-Platonic philosopher, regarded by the early Fathers as the bitterest and most dangerous enemy of the Church, wrote toward the end of the third century a work against Christianity in fifteen books, which was looked upon as the most powerful attack that had ever been made, and which called forth refutations from some of the greatest Fathers of the age: from Methodius of Tyre, Eusebius of Cæsarea, and Apollinaris of Laodicea; and even as late as the end of the fourth or beginning of the fifth century the historian Philostorgius thought it necessary to write another reply to it (see his H. E. X. 10). Porphyry's work is no longer extant, but the fragments of it which remain show us that it was both learned and skillful. He made much of the alleged contradictions in the Gospel records, and suggested difficulties which are still favorite weapons in the hands of skeptics. Like the work of Porphyry, and all the other refutations of it, the Apology of Eusebius has entirely perished. It is mentioned by Jerome (de vir. ill. 81 and Ep. ad Magnum, §3, Migne's ed. Ep. 70), by Socrates (H. E. III. 23), and by Philostorgius (H. E. VIII. 14). There is some dispute as to the number of books it contained. In his Ep. ad Magn. Jerome says that "Eusebius et Apollinaris viginti quinque, et triginta volumina condiderunt," which implies that it was composed of twenty-five books; while in his de ver. ill. 81, he speaks of thirty books, of which he had seen only twenty. Vallarsi says, however, that all his mss. agree in reading "twenty-five" instead of "thirty" in the latter passage, so that it would seem that the vulgar text is incorrect.
It is impossible to form an accurate notion of the nature and quality of Eusebius' refutation. Socrates speaks of it in terms of moderate praise ("which [i.e. the work of Porphyry] has been ably answered by Eusebius"), and Jerome does the same in his Ep. ad Magnum ("Alteri [i.e. Porphyry] Methodius, Eusebius, et Apollinaris fortissime responderunt"). At the same time the fact that Apollinaris and others still thought it necessary to write against Porphyry would seem to show that Eusebius' refutation was not entirely satisfactory. In truth, Jerome (Ep. ad Pammachium et Oceanum, §2, Migne's ed. Ep. 84) appears to rank the work of Apollinaris above that of Eusebius, and Philostorgius expressly states that the former far surpassed the latter (epi polu kratein egonismenon 'Eusebi& 251; kat' autou). The date of Eusebius' work cannot be determined. The fact that he never refers to it, although he mentions the work of Porphyry a number of times, has been urged by Valesius and others as proof that he did not write it until after 325 a.d.; but it is quite possible to explain his silence, as Lardner does, by supposing that his work was written in his earlier years, and that afterward he felt its inferiority and did not care to mention it. It seems, in fact, not unlikely that he wrote it as early, or even earlier than his work against Hierocles, at any rate before his attention was occupied with the Arian controversy and questions connected with it.
On the Numerous Progeny of the Ancients (peri tes ton palaion andron polupaidias). This work is mentioned by Eusebius in his Præp. Evang. VII. 8. 20 (Migne, Opera, III. 525), but by no one else, unless it be the book to which Basil refers in his De Spir. Sancto, 29, as Difficulties respecting the Polygamy of the Ancients. The work is no longer extant, but we can gather from the connection in which it is mentioned in the Præparatio, that it aimed at accounting for the polygamy of the Patriarchs and reconciling it with the ascetic ideal of the Christian life which prevailed in the Church of Eusebius' lifetime. It would therefore seem to have been written with an apologetic purpose.
Præparatio Evangelica (proparaskeue euangelike) and Demonstratio Evangelica ('Euangelike apodeixis). These two treatises together constitute Eusebius' greatest apologetic work. The former is directed against heathen, and aims to show that the Christians are justified in accepting the sacred books of the Hebrews and in rejecting the religion and philosophy of the Greeks. The latter endeavors to prove from the sacred books of the Hebrews themselves that the Christians do right in going beyond the Jews, in accepting Jesus as their Messiah, and in adopting another mode of life. The former is therefore in a way a preparation for the latter, and the two together constitute a defense of Christianity against all the world, Jews as well as heathen. In grandeur of conception, in comprehensiveness of treatment, and in breadth of learning, this apology undoubtedly surpasses all other apologetic works of antiquity. Lightfoot justly says, "This great apologetic work exhibits the same merits and defects which we find elsewhere in Eusebius. There is the same greatness of conception marred by the same inadequacy of execution, the same profusion of learning combined with the same inability to control his materials, which we have seen in his History. The divisions are not kept distinct; the topics start up unexpectedly and out of season. But with all its faults this is probably the most important apologetic work of the early Church. It necessarily lacks the historical interest of the apologetic writings of the second century; it falls far short of the thoughtfulness and penetration which give a permanent value to Origen's treatise against Celsus as a defense of the faith; it lags behind the Latin apologists in rhetorical vigor and expression. But the forcible and true conceptions which it exhibits from time to time, more especially bearing on the theme which may be briefly designated God in history,' arrest our attention now, and must have impressed his contemporaries still more strongly; while in learning and comprehensiveness it is without a rival." The wide acquaintance with classical literature exhibited by Eusebius in the Præparatio is very remarkable. Many writers are referred to whose names are known to us from no other source, and many extracts are given which constitute our only fragments of works otherwise totally lost. The Præparatio thus does for classical much what the History does for Christian literature.
A very satisfactory summary of the contents of the Præparatio is given at the beginning of the fifteenth book. In the first, second, and third books, the author exposes the absurdities of heathen mythology, and attacks the allegorical theology of the Neo-Platonists; in the fourth and fifth books he discusses the heathen oracles; in the sixth he refutes the doctrine of fate; in the seventh he passes over to the Hebrews, devoting the next seven books to an exposition of the excellence of their system, and to a demonstration of the proposition that Moses and the prophets lived before the greatest Greek writers, and that the latter drew their knowledge from the former; in the fourteenth and fifteenth books he exposes the contradictions among Greek philosophers and the vital errors in their systems, especially in that of the Peripatetics. The Præparatio is complete in fifteen books, all of which are still extant.
The Demonstratio consisted originally of twenty books (see Jerome's de vir. ill. 81, and Photius' Bibl. 10). Of these only ten are extant, and even in the time of Nicephores Callistus no more were known, for he gives the number of the books as ten (H. E. VI. 37). There exists also a fragment of the fifteenth book, which was discovered and printed by Mai (Script. vet. nova coll. I. 2, p. 173). In the first book, which is introductory, Eusebius shows why the Christians pursue a mode of life different from that of the Jews, drawing a distinction between Hebraism, the religion of all pious men from the beginning, and Judaism, the special system of the Jews, and pointing out that Christianity is a continuation of the former, but a rejection of the latter, which as temporary has passed away. In the second book he shows that the calling of the Gentiles and the repudiation of the Jews are foretold in Scripture. In books three to nine he discusses the humanity, divinity, incarnation, and earthly life of the Saviour, showing that all were revealed in the prophets. In the remainder of the work we may assume that the same general plan was followed, and that Christ's death, resurrection, and ascension, and the spread of his Church, were the subjects discussed in this as in nearly all works of the kind.
There is much dispute as to the date of these two works. Stroth and Cave place them after the Council of Nicæa, while Valesius, Lightfoot, and others, assign them to the ante-Nicene period. In two passages in the History Eusebius has been commonly supposed to refer to the Demonstratio (H. E. I. 2 and 6), but it is probable that the first, and quite likely the second also, refers to the Eclogæ Proph. We can, therefore, base no argument upon those passages. But in Præp. Evang. XII. 10 (Opera, III. 969) there is a reference to the persecution, which seems clearly to imply that it was still continuing; and in the Demonstratio (III. 5 and IV. 6; Opera, IV. 213 and 307), which was written after the Præparatio, are still more distinct indications of the continuance of the persecution. On the other hand, in V. 3 and VI. 20 (Opera, IV. 364 and 474) there are passages which imply that the persecution has come to an end. It seems necessary then to conclude, with Lightfoot, that the Demonstratio was begun during the persecution, but not completed until peace had been established. The Præparatio, which was completed before the Demonstratio was begun (see the prooemium to the latter), must have been finished during the persecution. It contains in X. 9 (Opera, III. 807) a reference to the Chronicle as an already published work (see above, p. 31).
The Præparatio and Demonstratio are found in Migne's edition of the Opera, III. and IV. 9 sq. A more recent text is that of Dindorf in Teubner's series, 1867. The Præparatio has been published separately by Heinichen, 2 vols., Lips. 1842, and by Gaisford, 4 vols., Oxon. 1843. The latter contains a full critical apparatus with Latin translation and notes, and is the most useful edition which we have. Seguier in 1846 published a French translation with notes. The latter are printed in Latin in Migne's edition of the Opera, III. 1457 sq. The French translation I have not seen.
The Demonstratio was also published by Gaisford in 2 vols., Oxon. 1852, with critical apparatus and Latin translation. Hænell has made the two works the subject of a monograph entitled De Eusebio Cæsariensi religionis Christianæ Defensore (Gottingæ, 1843) which I know only from the mention of it by Stein and Lightfoot.
Præparatio Ecclesiastica ('Ekklesiastike Proparaskeue), and Demonstratio Ecclesiastica ('Ekklesiastike 'Apodeixis). These two works are no longer extant. We know of the former only from Photius' reference to it in Bibl. 11, of the latter from his mention of it in Bibl. 12.
Lightfoot says that the latter is referred to also in the Jus Græco-Romanum (lib. IV. p. 295; ed. Leunclav.). We know nothing about the works (except that the first according to Photius contained extracts), and should be tempted to think them identical with the Præparatio and Demonstratio Evang. were it not that Photius expressly mentions the two latter in another part of his catalogue (Bibl. 10). Lightfoot supposes that the two lost works did for the society what the Præp. and Dem. Evang. do for the doctrines of which the society is the depositary, and he suggests that those portions of the Theophania (Book IV.) which relate to the foundation of the Church may have been adopted from the Dem. Ecclesiastica, as other portions of the work (Book V.) are adopted from the Dem. Evang.
If there is a reference in the Præp. Evang. I. 3 (Opera, III. 33) to the Demonstratio Eccles., as Lightfoot thinks there may be, and as is quite possible, the latter work, and consequently in all probability the Præp. Eccles. also, must have been written before 313 a.d.
Two Books of Objection and Defense ('Elenchou kai 'Apologias logoi duo). These are no longer extant, but are mentioned by Photius in his Bibl. 13. We gather from Photius' language that two editions of the work were extant in his time. The books, as Photius clearly indicates, contained an apology for Christianity against the attacks of the heathen, and not, as Cave supposed, a defense of the author against the charge of Arianism. The tract mentioned by Gelasius of Cyzicus (see below, p. 64) is therefore not to be identified with this work, as Cave imagined that it might be.
Theophaniaor Divine Manifestation (theoph?neia). A Syriac version of this work is extant in the same ms. which contains the Martyrs of Palestine, and was first published by Lee in 1842. In 1843 the same editor issued an English translation with notes and extended prolegomena (Cambridge, 1 vol.). The original work is no longer extant in its entirety, but numerous Greek fragments were collected and published by Mai in 1831 and 1833 (Script. vet. nov. coll. I. and VIII.), and again with additions in 1847 (Bibl. Nova Patrum, IV. 110 and 310; reprinted by Migne, Opera, VI. 607-690. Migne does not give the Syriac version). The manuscript which contains the Syriac version was written in 411, and Lee thinks that the translation itself may have been made even during the lifetime of Eusebius. At any rate it is very old and, so far as it is possible to judge, seems to have reproduced the sense of the original with comparative accuracy. The subject of the work is the manifestation of God in the incarnation of the Word. It aims to give, with an apologetic purpose, a brief exposition of the divine authority and influence of Christianity. It is divided into five books which handle successively the subject and the recipients of the revelation, that is, the Logos on the one hand, and man on the other; the necessity of the revelation; the proof of it drawn from its effects; the proof of it drawn from its fulfillment of prophecy; finally, the common objections brought by the heathen against Christ's character and wonderful works. Lee says of the work: "As a brief exposition of Christianity, particularly of its Divine authority, and amazing influence, it has perhaps never been surpassed." "When we consider the very extensive range of inquiry occupied by our author, the great variety both of argument and information which it contains, and the small space which it occupies; we cannot, I think, avoid coming to the conclusion, that it is a very extraordinary work, and one which is as suitable to our own times as it was to those for which it was written. Its chief excellency is, that it is argumentative, and that its arguments are well grounded, and logically conducted."