His distinction between roductive and unproductive labour has led to errors, ib. His account of the influence of exchange on labour commended, 105. Wrong in representing the principle of value as residing in materiality and durability, 136. Quoted and controverted on the subject of value, 156. Opinions on landed property quoted, 252. Social Motive Force described and explained, 495-503. Personal interest is the social motive force which leads us to shun evil and seek after good, 495. Attraction towards happiness and repulsion from pain, the mainspring of the social mechanism, 496. This impulsive force is under direction of our intelligence, and intelligence may err, ib. The laws of responsibility and solidarity lend assistance to repress error and injustice, 497. Attempts of the Socialists to substitute devotion and self-sacrifice for personal interest, as the social motive force, combated, 498, 499. Socialist works and writers referred to, 500-503. Social Problem, demands solution, 33, 34. Solution to be found in liberty, not in constraint, 35. The man who demonstrates that the good of each tends to the good of all, as the good of all tends to the good of each, will have resolved the social problem, 118. Socialists differ from Economists in regarding man's interests as antagonistic, 35. Socialist works referred to, 64, and note. Society, mechanism of, 48. Gives the humblest mechanic more in one day than he could himself produce in many ages, ib. Study of, the business of Political Economy, 51. In social state our powers exceed our wants, 98. Solidarity is collective responsibility, 488. Not of legislative creation, as represented by Rousseau, 488, 489. The philosophers of the last century did not believe in it, 489. Instances in which individuals suffer from the errors or faults of others-this is the law of solidarity, 489, 490. Responsibility is not exclusively personal, but is shared and divided, 490. Society, in turn, suffers from the errors or faults of individuals, and the law of solidarity comes to check such actions, 491. Solidarity, like responsibility, is a progressive force, and resolves itself into repercussive or reflected responsibility, ib. To enable those who suffer from another's acts to react against them, connexion between cause and effect should be known, 492. Not always known, from the circumstance that the first effect may seem good, though all the subsequent consequences are bad, ib. Example of this in case of war, ib. In the case of slavery, of religious errors, and of prohibition, ib. Human law should coincide with the natural law, and organize reaction, 493.