Eusebius' summary of salvation history

Even when you are used to them, the early Christian post-biblical writings tend to make for difficult reading. They have a tendency to not be very succinct or clear and to discuss every point in the context of half a dozen obscure Old Testament quotes understood allegorically. It makes it passages which are clear and concise all the nicer. Here is one such passage from Eusebius, spelling out the Christian system of salvation.
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Eusebius, ~320AD, Proof of the Gospel (Demonstratio Evangelica) Book 8, intro:
I have already, you will remember, accounted for the Christ coming in these last times and not long ago, but I will here shortly repeat myself.

In the old days the souls of men were tyrannized over by squalid folly and sin, and a strange godlessness ruled over all human life, so that men were like wild and untamed beasts. They knew nothing of cities, or constitutions, or laws, nor anything honourable or progressive; they set no store on arts and sciences, they had no conception of virtue and philosophy, they lived in lonely deserts, in mountains, caves, and villages; they preyed on their neighbours like robbers, and gained their livelihood mostly by tyrannizing over those weaker than themselves. But though they did not know the Supreme God, nor the path of true religion, yet inspired by conceptions of natural religion they agreed in self-taught principles about the existence of a divine power, regarded it as and called it God, and considered the name one of salvation and beneficence, but they were not yet able to realize anything beyond a Being transcending the world of visible nature. Wherefore some of them----

"worshipped and served the creature rather than the creator; and they became vain in their imaginations, and their foolish heart was darkened; and they changed the glory of the incorruptible God into an image made like unto corruptible man, and to birds and four-footed beasts and creeping things."

And so they made images of their kings and tyrants long dead, and paid them divine honours, and by imputing divinity to them sanctified their wicked and lustful deeds as works of the gods.

How could the wise and good word of Christ, instilling the quintessence of wisdom, be in harmony with men in that condition, and involved in such depths of evil? So that holy and all-seeing Justice, pruning them like a wild and dangerous wood, now afflicted them by floods, now by fire, now delivered them to wars, butchery and sieges at one another's hands, urged on as they were to war against each other by those very daemons whom they regarded as their gods, with the result that human life in those days admitted no neighbourly intercourse, mutual association or union. Those were few, as might be expected in such days, and easily numbered, who, as the Hebrew oracles tell us, were found to be godly; with such, Justice met by the use of oracles and theophanies, she took them by the hand and cared for them with the elementary but helpful Mosaic legislation.

But when at last by the legislation laid down for them, and by the later teaching of the prophets poured out like a sweet smell upon all men, the character of the people became civilized, and constitutions and legal systems were established among most nations, and the name of virtue and philosophy became popularly honoured, as if their old savagery had ceased and their wild and cruel life were transferred to something gentler: then at length, at the fitting time, the perfect and heavenly teacher of perfect and heavenly thoughts and teaching, the leader to the true knowledge of God, God the Word, revealed Himself, at the time announced for His Incarnation, preaching the Gospel of the Father's love, the same for all nations, whether Greeks or Barbarians, to every race of men, moving all to a common salvation in God, promising the truth and light of true religion, the kingdom of Heaven, and eternal life to all.

Such, then, is my account of the reasons why the Christ of God shone forth on all men now and not long ago.