Not long ago, a distinguished political scientist called attention to “the law of the pendulum” in politics. No sooner, he argued, does a broad political tendency establish itself than tendencies of opposite direction set in and gather force until the original tendency is reversed. As applied to relatively short periods of time and to movements which reflect temporary trends, a plausible case can be made out for the law of the pendulum. It seems doubtful, however, whether it can be proved with like plausibility for tendencies which are truly secular. Take as an example the steady trend toward enlarging the size of the independent political unit, or state. Since the feudal age, the tendency has run in the same direction, sometimes more slowly and sometimes more rapidly, but with seldom a check, and never a retreat, from the feudal state to the national state, from the national state to the colonial empire, and in recent years from the colonial empire toward some larger goal of world organization. Barring accidental destruction of modern machine civilization, a recurrence to a world of petty states seems unthinkable.

Whether or not the law of the pendulum applies in the world of political events, there can be no doubt of its sway over political thought. No sooner does a doctrine embody itself in an institution than it exposes its nakedness in a pillory and challenges competing dogmas to do their worst. In consequence, the history of political ideas has been a story of oscillations, of attack and repulse and counter-attack.