Montesquieu

Island peo­ples have more affi­nity for liberty than conti­nen­tal peo­ples. Islands are ordi­na­rily rela­ti­vely small1 ; part of the peo­ple can­not be so well employed oppres­sing the rest ; the sea sepa­ra­tes them from the great empi­res, and one tyranny can­not come to the aid of ano­ther ; conque­rors are hal­ted by the sea, the islan­ders are not caught up in the conquest, and more easily pre­serve their laws.

Japan is an exception to this by virtue of its size and its servitude.