Thus in the middle ages there was, with a large number of cities, a decisive moment when the building of city halls and cathedrals became a violent passion, which had to be satisfied at any price; the life of the community depended upon it. Security and strength, public order, centralization, nationality, country, independence, these are the elements which make up the life of society, the totality of its mental faculties; these are the sentiments which must find expression and representation. Such formerly was the object of the temple of Jerusalem, real palladium of the Jewish nation; such was the temple of Jupiter Capitolinus of Rome. Later, after the municipal palace and the temple,--organs, so to speak, of centralization and progress,--came the other works of public utility,--bridges, theatres, schools, hospitals, roads, etc. The monuments of public utility being used essentially in common, and consequently gratuitously, society is rewarded for its advances by the political and moral advantages resulting from these great works, and which, furnishing security to labor and an ideal to the mind, give fresh impetus to industry and the arts. But it is different with the articles of domestic consumption, which alone fall within the category of exchange. These can be produced only upon the conditions of mutuality which make consumption possible,--that is, immediate payment with advantage to the producers. These conditions we have developed sufficiently in the theory of proportionality of values, which we might call as well the theory of the gradual reduction of cost. I have demonstrated theoretically and by facts the principle that ALL LABOR SHOULD LEAVE AN EXCESS; but this principle, as certain as any proposition in arithmetic, is very far from universal realization. While, by the progress of collective industry, each individual day's labor yields a greater and greater product, and while, by necessary consequence, the laborer, receiving the same wages, must grow ever richer, there exist in society classes which THRIVE and classes which PERISH; laborers paid twice, thrice, a hundred times over, and laborers continually out of pocket; everywhere, finally, people who enjoy and people who suffer, and, by a monstrous division of the means of industry, individuals who consume and do not produce. The distribution of well-being follows all the movements of value, and reproduces them in misery and luxury on a frightful scale and with terrible energy. But everywhere, too, the progress of wealth--that is, the proportionality of values--is the dominant law; and when the economists combat the complaints of the socialists with the progressive increase of public wealth and the alleviations of the condition of even the most unfortunate classes, they proclaim, without suspecting it, a truth which is the condemnation of their theories.