For some of the ancients [Parmenides and Zeno] thought that what is must necessarily be one and motionless, since the void is non-existent and there could be no motion without a separately existing void, and again there could not be a plurality without something to separate them. And if someone thinks the universe is not continuous but consists of divided pieces in contact with each other, this is no different, they held, from saying that it is many, not one, and is void. For if it is divisible everywhere, there is no unit, and therefore no many, and the whole is void. If on the hand it is divisible in one place and not another, this seems like a piece of fiction. For how far is it divisible, and why is one part of the whole like this -- full -- and another part divided? Again, it is necessary similarly that there be no motion...