To us, however, with whom it is impossible for all these things to come aptly at one and the same time, namely, the moon's fourteenth, and the Lord's day, and the passing of the equinox, and whom the obligation of the Lord's resurrection binds to keep the Paschal festival on the Lord's day, it is granted that we may extend the beginning of our celebration even to the moon's twentieth. For although the moon of the 20th does not fill the whole night, yet, rising as it does in the second watch, it illumines the greater part of the night. Certainly if the rising of the moon should be delayed on to the end of two watches, that is to say, to midnight, the light would not then exceed the darkness, but the darkness the light. But it is clear that in the Paschal feast it is not possible that any part of the darkness should surpass the light; for the festival of the Lord's resurrection is one of light, and there is no fellowship between light and darkness. And if the moon should rise in the third watch, it is clear that the 22d or 23d of the moon would then be reached, in which it is not possible that there can be a true celebration of Easter. For those who determine that the festival may be kept at this age of the moon, are not only unable to make that good by the authority of Scripture, but turn also into the crime of sacrilege and contumacy, and incur the peril of their souls; inasmuch as they affirm that the true light may be celebrated along with something of that power of darkness which dominates all.