75 You may object and rejoin, Why was the Saviour sent forth so late? In unbounded, eternal ages, we reply, nothing whatever should be spoken of as late. For where there is no end and no beginning, nothing is too soon, nothing too late. For time is perceived from its beginnings and endings, which an unbroken line and endless succession of ages cannot have. For what if the things themselves to which it was necessary to bring help, required that as a fitting time?
For what if the condition of antiquity was different from that of later times? What if it was necessary to give help to the men of old in one way, to provide for their descendants in another? Do you not hear your own writings read, telling that there were once men who were demi-gods, heroes with immense and huge bodies? Do you not read that infants on their mothers' breasts shrieked like. Stentors, whose bones, when dug up in different parts of the earth, have made the discoverers almost doubt that they were the remains of human limbs?
So, then, it may be that Almighty God, the only God, sent forth Christ then indeed, after that the human race, becoming feebler, weaker, began to be such as we are. If that which has been done now could have been done thousands of years ago, the Supreme Ruler would have done it; or if it had been proper, that what has been done now should be accomplished as many thousands after this, nothing compelled God to anticipate the necessary lapse of time. His plans are executed in fixed ways; and that which has been once decided on, can in no way be changed again.
Source: Against the Heathen (New Advent)