48 But some one will perhaps say that the care of such a god has been denied to later and following ages, because the ways in which men now live are impious and objectionable; that it brought help to our ancestors, on the contrary, because they were blameless and guiltless. Now this might perhaps have been listened to, and said with some reasonableness, either if in ancient times all were good without exception, or if later times produced only wicked people, and no others. But since this is the case that in great peoples, in nations, nay, in all cities even, men have been of mixed natures, wishes, man-nets, and the good and bad have been able to exist at the same time in former ages, as well as in modern times, it is rather stupid to say that mortals of a later day have not obtained the aid of the deities on account of their wickedness.
For if on account of the wicked of later generations the good men of modern times have not been protected, on account of the ancient evil-doers also the good of former times should in like manner not have gained the favour of the deities. But if on account of the good of ancient times the wicked of ancient times were preserved also, the following age, too, should have been protected, although it was faulty, on account of the good of later times. So, then, either that snake gained the reputation of being a deliverer while he had been of no service at all, through his being brought to the city when the violence of the disease was already weakened and impaired, or the hymns of the fates must be said to have been far from giving true indications, since the remedy given by them is found to have been useful, not to all in succession, but to one age only.
Source: Against the Heathen (New Advent)