"The theory of Parmenides is the inevitable outcome of a corporeal monism, and his bold declaration of it ought to have destroyed that theory... If he had lacked courage to work out the prevailing views... to their logical conclusion... men might have gone on in the endless circle of opposition, rarefaction and condensation, one and many, for ever. ...[T]he thoroughgoing dialectic of Parmenides ...made progress possible. Philosophy must now cease [either] to be monistic or... corporealist. It could not cease to be corporealist; for the incorporeal was still unknown. It therefore ceased to be monistic, and arrived at the atomic theory... matter in motion."