Beyond notices in his extant writings, the major sources are the 5th-century ecclesiastical historians Socrates, Sozomen, and Theodoret, and the 4th-century Christian author Jerome.

[16] Some, like theologian and ecclesiastical historian John Henry Newman, understand Eusebius's statement that he had heard Dorotheus of Tyre "expound the Scriptures wisely in the Church" to indicate that Eusebius was Dorotheus's pupil while the priest was resident in Antioch; others, like the scholar D. S. Wallace-Hadrill, deem the phrase too ambiguous to support the contention.

[20] Together with the books of his patron Ambrosius, Origen's library (including the original manuscripts of his works[21][note 4]) formed the core of the collection that Pamphilus established.

[25] He was compared to Demetrius of Phalerum—as well as to another (evidently, learnèd) scholar by the name of "Pisistratus"[note 5]—for Pamphilus had gathered Bibles "from all parts of the world".

[28] Marginal comments in extant manuscripts note that Pamphilus and his friends and pupils, including Eusebius, corrected and revised much of the biblical text in their library.

[37] Soon after joining Pamphilus's school, Eusebius started helping his master expand the library's collections and broaden access to its resources.

[citation needed] After the Emperor's death (c. 337), Eusebius wrote the Life of Constantine, an important historical work because of eyewitness accounts and the use of primary sources.

Christianity at last found recognition by the State; and this brought new problems – apologies of a different sort had to be prepared.

To all this activity must be added numerous writings of a miscellaneous nature, addresses, letters, and the like, and exegetical works that extended over the whole of his life and that include both commentaries and an important treatise on the location of biblical place names and the distances between these cities.

The first part, the Chronography (Χρονογραφία (Chronographia)), gives an epitome of universal history from the sources, arranged according to nations.

[46] Although its accuracy and biases have been questioned,[47] it remains an important source on the early church due to Eusebius's access to materials now lost.

[48] Eusebius's Life of Constantine (Vita Constantini) is a eulogy or panegyric, and therefore its style and selection of facts are affected by its purpose, rendering it inadequate as a continuation of the Church History.

As the historian Socrates Scholasticus said, at the opening of his history which was designed as a continuation of Eusebius, "Also in writing the life of Constantine, this same author has but slightly treated of matters regarding Arius, being more intent on the rhetorical finish of his composition and the praises of the emperor than on an accurate statement of facts."

Writing after Constantine had died, Eusebius claimed that the emperor himself had recounted to him that some time between the death of his father – the augustus Constantius – and his final battle against his rival Maxentius as augustus in the West, Constantine experienced a vision in which he and his soldiers beheld a Christian symbol, "a cross-shaped trophy formed from light", above the sun at midday.

A work on the martyrs of Palestine in the time of Diocletian was composed after 311; numerous fragments are scattered in legendaries which have yet to be collected.

This work was recently (2011) translated into the English language by David J. Miller and Adam C. McCollum and was published under the name Eusebius of Caesarea: Gospel Problems and Solutions.

Now there were among the Hebrews three outstanding offices of dignity, which made the nation famous, firstly the kingship, secondly that of prophet, and lastly the high priesthood.

And that the proofs that the times had come, would lie in the ceasing of the Mosaic worship, the desolation of Jerusalem and its Temple, and the subjection of the whole Jewish race to its enemies.

...The holy oracles foretold that all these changes, which had not been made in the days of the prophets of old, would take place at the coming of the Christ, which I will presently shew to have been fulfilled as never before in accordance with the predictions" (Demonstratio Evangelica VIII).

Eusebius said: The Creator of all things has impressed a natural law upon the soul of every man, as an assistant and ally in his conduct, pointing out to him the right way by this law; but, by the free liberty with which he is endowed, making the choice of what is best worthy of praise and acceptance, he has acted rightly, not by force, but from his own free-will, when he had it in his power to act otherwise, As, again, making him who chooses what is worst, deserving of blame and punishment, because he has by his own motion neglected the natural law, and becoming the origin and fountain of wickedness, and misusing himself, not from any extraneous necessity, but from free will and judgment.

[59] A letter Eusebius is supposed to have written to Constantine's daughter Constantina, refusing to fulfill her request for images of Christ, was quoted in the decrees (now lost) of the Iconoclast Council of Hieria in 754, and later quoted in part in the rebuttal of the Hieria decrees in the Second Council of Nicaea of 787, now the only source from which some of the text is known.

[60] In the June 2002 issue of the Church History journal, Pier Franco Beatrice reports that Eusebius testified that the word homoousios (consubstantial) "was inserted in the Nicene Creed solely by the personal order of Constantine.

"[61] According to Eusebius of Caesarea, the word homoousios was inserted in the Nicene Creed solely by the personal order of Constantine.

It is very difficult to explain the seeming paradoxical fact that this word, along with the explanation given by Constantine, was accepted by the "Arian" Eusebius, whereas it has left no traces at all in the works of his opponents, the leaders of the anti-Arian party such as Alexander of Alexandria, Ossius of Cordova, Marcellus of Ancyra, and Eustathius of Antioch, who are usually considered Constantine's theological advisers and the strongest supporters of the council.

Having once excluded any relationship of the Nicene homoousios with the Christian tradition, it becomes legitimate to propose a new explanation, based on an analysis of two pagan documents which have so far never been taken into account.

As can be clearly seen in the Poimandres, and even more clearly in an inscription mentioned exclusively in the Theosophia, in the theological language of Egyptian paganism the word homoousios meant that the Nous-Father and the Logos-Son, who are two distinct beings, share the same perfection of the divine nature.However, the council evidently did not force the insertion of the word and instead adopted a text related to the confession of Jerusalem.

[63] Alternate views have suggested that Gibbon's dismissal of Eusebius is inappropriate: While many have shared Burckhardt's assessment, particularly with reference to the Life of Constantine, others, while not pretending to extol his merits, have acknowledged the irreplaceable value of his works which may principally reside in the copious quotations that they contain from other sources, often lost.

The man indeed is very worthy of being remembered in these times, both for his skill in many things, and for his wonderful genius, and by both Gentiles and Christians he was held distinguished and most noble among philosophers.

At the same time he has written many things, but especially the following books: The Præparatio Evangelica, the Ecclesiastical History, Against Porphyry, a very bitter enemy of the Christians; he has also composed Six Apologies in Behalf of Origen, a Life of Pamphilus the Martyr, from whom on account of friendship he took his surname, in three books; likewise very learned Commentaries on the hundred and fifty Psalms.

A bone fragment relic of Eusebius within its original reliquary is on display at the Shrine of All Saints located within St. Martha's Catholic Church in Morton Grove, Illinois.