In this condition of the world, theory and action follow close upon each other, and practical evils easily give birth to opposite systems. In the realms of free-will, the regularity of natural progress is preserved by the conflict of extremes. The impulse of the reaction carries men from one extremity towards another. The pursuit of a remote and ideal object, which captivates the imagination by its splendour and the reason by its simplicity, evokes an energy which would not be inspired by a rational, possible end, limited by many antagonistic claims, and confined to what is reasonable, practicable, and just. One excess or exaggeration is the corrective of the other, and error promotes truth, where the masses are concerned, by counterbalancing a contrary error. The few have not strength to achieve great changes unaided; the many have not wisdom to be moved by truth unmixed. Where the disease is various, no particular definite remedy can meet the wants of all. Only the attraction of an abstract idea, or of an ideal state, can unite in a common action multitudes who seek a universal cure for many special evils, and a common restorative applicable to many different conditions. And hence false principles, which correspond with the bad as well as with the just aspirations of mankind, are a normal and necessary element in the social life of nations. Theories of this kind are just, inasmuch as they are provoked by definite ascertained evils, and undertake their removal. They are useful in opposition, as a warning or a threat, to modify existing things, and keep awake the consciousness of wrong. They cannot serve as a basis for the reconstruction of civil society, as medicine cannot serve for food; but they may influence it with advantage, because they point out the direction, though not the measure, in which reform is needed. They oppose an order of things which is the result of a selfish and violent abuse of power by the ruling classes, and of artificial restriction on the natural progress of the world, destitute of an ideal element or a moral purpose. Practical extremes differ from the theoretical extremes they provoke, because the first are both arbitrary and violent, whilst the last, though also revolutionary, are at the same time remedial. In one case the wrong is voluntary, in the other it is inevitable. This is the general character of the contest between the existing order and the subversive theories that deny its legitimacy. There are three principal theories of this kind, impugning the present distribution of power, of property, and of territory, and attacking respectively the aristocracy, the middle class, and the sovereignty. They are the theories of equality, communism, and nationality. Though sprung from a common origin, opposing cognate evils, and connected by many links, they did not appear simultaneously. Rousseau proclaimed the first, Baboeuf the second, Mazzini the third; and the third is the most recent in its