surrounded it later arose,--it still was a step forward, a distinct advance upon the older customs of cannibalism and wholesale slaughter. Nor was it a progressive step only on the humanitarian side. It had other, profounder consequences from the evolutionary point of view. It made a leisure class possible, and provided the only conditions under which art, philosophy, and jurisprudence could be evolved. The secret of Aristotle's saying, that only by the invention of machines would the abolition of slavery ever be made possible, lies in his recognition of the fact that the labor of slaves alone made possible the devotion of a class of men to the pursuit of knowledge instead of to the production of the primal necessities of life. The Athens of Pericles, for example, with all its varied forms of culture, its art and its philosophy, was a semi-communism of a caste above, resting upon a basis of slave labor underneath. Similar conditions prevailed in all the so-called ancient democracies of civilization. The private ownership of wealth producers and their products made private exchange inevitable; individual ownership of land took the place of communal ownership, and a monetary system was invented. Here, then, in the private ownership of land and laborer, private production and exchange, we have the economic factors which caused the great revolts of antiquity, and led to that concentration of wealth into few hands, with its resulting mad luxury on the one hand and widespread proletarian misery upon the other, which conspired to the overthrow of Greek and Roman civilization. The study of those relentless economic forces which led to the break-up of Roman civilization is important as showing how chattel slavery became modified and the slave to be regarded as a serf, a servant bound to the soil. The lack of adequate production, the crippling of commerce by hordes of corrupt officials, the overburdening of the agricultural estates with slaves, so that agriculture became profitless, the crushing out of free labor by slave labor, and the rise of a wretched class of freemen proletarians, these, and other kindred causes, led to the breaking up of the great estates; the dismissal of superfluous slaves, in many cases, and the partial enfranchisement of others by making them hereditary tenants, paying a fixed share of their product as rent--here we have the embryonic stage of feudalism. It was a revolution, this transformation of the social system of Rome, of infinitely greater importance than the sporadic risings of a few thousand slaves. Yet, such is the lack of perspective which the historians have shown, it is given a far less important place in the histories than the risings in question. Slavery, chattel slavery, died because it had ceased to be profitable; serf labor arose because it was more profitable. Slave labor was economically impossible, and the labor of free men was morally impossible; it had, thanks to the slave system,