Celsus, in the next place, suspecting, or perhaps seeing clearly enough, the answer which might be returned by those who defend the destruction of men by the deluge, continues: “But if he does not destroy his own offspring, whither does he convey them out of this world which he himself created?” To this we reply, that God by no means removes out of the whole world, consisting of heaven and earth, those who suffered death by the deluge, but removes them from a life in the flesh, and, having set them free from their bodies, liberates them at the same time from an existence upon earth, which in many parts of Scripture it is usual to call the “world.”
In the Gospel according to John especially, we may frequently find the regions of earth termed “world,” as in the passage, “He was the true Light, which lightens every man that comes into the 'world;'” as also in this, “In the world you shall have tribulation; but be of good cheer, I have overcome the world.” If, then, we understand by “removing out of the world” a transference from “regions on earth,” there is nothing absurd in the expression. If, on the contrary, the system of things which consists of heaven and earth be termed “world,” then those who perished in the deluge are by no means removed out of the so-called “world.”
And yet, indeed, if we have regard to the words, “Looking not at the things which are seen, but at the things which are not seen;” and also to these, “For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made,” — we might say that he who dwells amid the “invisible” things, and what are called generally “things not seen,” is gone out of the world, the Word having removed him hence, and transported him to the heavenly regions, in order to behold all beautiful things.
Source: Against Celsus (New Advent)