Customs have often been broken up by the clashing of different societies; but in that case they merely crystallize again into new shapes.

But to break through custom by the sheer force of reflection, and so to make rational progress possible, was the intellectual feat of one people, the ancient Greeks; and it is at least highly doubtful if, without their leadership, a progressive civilization would have existed to-day.
It may be added in parenthesis that customs may linger on indefinitely, after losing, through one cause or another, their place amongst the vital interests of the community.

They are, or at any rate seem, harmless; their function is spent.

Hence, whilst perhaps the humbler folk still take them more or less seriously, the leaders of society are not at pains to suppress them.

Nor would they always find it easy to do so.