30 1What proof then have we that the structure was not already completed? First, self-evident facts. No part of the earth can possibly touch the heaven for the reason already mentioned, namely that it is just as impossible as it is for the centre to touch the circumference. Secondly, because the aether, that holy fire, is an unquenchable flame, as its very name shews, derived as it is from αἴθειν, which is a special term for “burn.” 2This is attested by a single part of the heavenly expanse of fire, namely the Sun, which, in spite of its great distance, sends its rays to the corners of the earth, and both earth and the naturally cold extent of air, which divides it from the sphere of heaven, is warmed or consumed by it as the case may be. For to all that is at a long distance from its course or lies at an angle to it, it merely gives warmth, but all that is near it or directly under it it actually destroys with the force of its flames. If this is so, the men who ventured on the ascent could not fail to be blasted and consumed by the fire, leaving their vaulting ambition unfulfilled. 3That it was unfulfilled seems to be suggested by Moses in the words which follow. “They ceased,” he says, “building the city and the tower” (Gen. 11:8), obviously not because they had finished it, but because they were prevented from completing it by the confusion that fell upon them. 4Yet as the enterprise was not only planned but undertaken, they have not escaped the guilt which would attend its accomplishment.