He continues to say that “neither have visible things been given to man (by God), but each individual thing comes into existence and perishes for the sake of the safety of the whole passing agreeably to the change, which I have already mentioned, from one thing to another.” It is unnecessary, however, to linger over the refutation of these statements, which have been already refuted to the best of my ability. And the following, too, has been answered, viz., that “there will neither be more nor less good and evil among mortals.”
This point also has been referred to, viz., that “God does not need to amend His work afresh.” But it is not as a man who has imperfectly designed some piece of workmanship, and executed it unskilfully, that God administers correction to the world, in purifying it by a flood or by a conflagration, but in order to prevent the tide of evil from rising to a greater height; and, moreover, I am of opinion that it is at periods which are precisely determined beforehand that He sweeps wickedness away, so as to contribute to the good of the whole world. If, however, he should assert that, after the disappearance of evil, it again comes into existence, such questions will have to be examined in a special treatise. It is, then, always in order to repair what has become faulty that God desires to amend His work afresh.
For although, in the creation of the world, all things had been arranged by Him in the most beautiful and stable manner, He nevertheless needed to exercise some healing power upon those who were labouring under the disease of wickedness, and upon a whole world, which was polluted as it were thereby. But nothing has been neglected by God, or will be neglected by Him; for He does at each particular juncture what it becomes Him to do in a perverted and changed world. And as a husbandman performs different acts of husbandry upon the soil and its productions, according to the varying seasons of the year, so God administers entire ages of time, as if they were, so to speak, so many individual years, performing during each one of them what is requisite with a reasonable regard to the care of the world; and this, as it is truly understood by God alone, so also is it accomplished by Him.
Source: Against Celsus (New Advent)