'War,' says Machiavelli, 'ought to be the only study of a prince' and by a prince he means every sort of state, however constituted. 'He ought,' says this great political doctor, 'to consider peace only as a breathing-time, which gives him leisure to contrive, and furnishes ability to execute military plans. 'A meditation on the conduct of political societies made old Hobbes imagine that war was the state of nature.