You may think the title of the work somewhat ambitious; and assuredly I make no pretension to reveal the designs of Providence in the social order, and to explain the mechanism of all the forces with which God has endowed man for the realization of progress. All that I have aimed at is to put you on the right track, and make you acquainted with the truth, that ‹all legitimate interests are in harmony›. That is the predominant idea of my work, and it is impossible not to recognise its importance. For some time it has been the fashion to laugh at what has been called the ‹social problem›: and no doubt some of the solutions which have been proposed afford but too much ground for raillery. But in the problem itself there is nothing laughable. It is the ghost of Banquo at the feast of Macbeth—and no dumb ghost either; for in formidable accents it calls out to terror-stricken society—a solution or death! [p034] Now this solution, you will at once see, must be different according as men’s interests are held to be naturally harmonious or naturally antagonistic. In the one case, we must seek for the solution in Liberty—in the other, in Constraint. In the one case, we have only to be passive—in the other, we must necessarily offer opposition. But Liberty assumes only one shape. Once convinced that each of the molecules which compose a fluid possesses in itself the force by which the general level is produced, we conclude that there is no surer or simpler way of seeing that level realized than not to interfere with it. All, then, who set out with this fundamental principle, that ‹men’s interests are harmonious›, will agree as to the practical solution of the social problem,—to abstain from displacing or thwarting those interests. Constraint, on the other hand, may assume a thousand shapes, according to the views which we take of it, and which are infinitely varied. Those schools which set out with, the principle, that ‹men’s interests are antagonistic›, have done nothing yet towards the solution of the problem, unless it be that they have thrust aside Liberty. Among the infinite forms of Constraint, they have still to choose the one which they consider good, if indeed any of them be so. And then, as a crowning difficulty, they have to obtain universal acceptance, among men who are free agents, for the particular form of Constraint to which they have awarded the preference. But, on this hypothesis, if human interests are, by their very nature, urged into fatal collision, and if this shock can be avoided only by the accidental invention of an artificial social order, the destiny of the human race becomes very hazardous, and we ask in terror, 1st, If any man is to be found who has discovered a satisfactory form of Constraint? 2d, Can this man bring to his way of thinking the innumerable schools who give the preference to other forms? 3d, Will mankind give in to that particular form which, by hypothesis, runs counter to all individual interests?