7. We can scarcely do better, in fine, than follow Plato. Thus:
In the universe as a whole there must necessarily be such a degree of solidity, that is to say, of resistance, as will ensure that the earth, set in the centre, be a sure footing and support to the living beings moving over it, and inevitably communicate something of its own density to them: the earth will possess coherence by its own unaided quality, but visibility by the presence of fire: it will contain water against the dryness…