Plato's 'ideas' became the formulae of a system of magic, and the command of Jesus that one should give all that one had to the poor handed over one-third of the land of Europe to be the untaxed property of wealthy ecclesiastics.
It is this last relation between words and things which makes the central difficulty of thought about politics.

The words are so rigid, so easily personified, so associated with affection and prejudice; the things symbolised by the words are so unstable.

The moralist or the teacher deals, as a Greek would say, for the most part, with 'natural,' the politician always with 'conventional' species.

If one forgets the meaning of motherhood or childhood, Nature has yet made for us unmistakable mothers and children who reappear, true to type, in each generation.

The chemist can make sure whether he is using a word in precisely the same sense as his predecessor by a few minutes' work in his laboratory.