Along with these three kinds of law goes a fourth, most important of all, which is not graven on tablets of marble or brass, but on the hearts of the citizens. This forms the real constitution of the State, takes on every day new powers, when other laws decay or die out, restores them or takes their place, keeps a people in the ways in which it was meant to go, and insensibly replaces authority by the force of habit. I am speaking of morality, of custom, above all of public opinion; a power unknown to political thinkers, on which none the less success in everything else depends. With this the great legislator concerns himself in secret, though he seems to confine himself to particular regulations; for these are only the arc of the arch, while manners and morals, slower to arise, form in the end its immovable keystone.

Among the different classes of laws, the political, which determine the form of the government, are alone relevant to my subject.