adam smith was skeptical of slavery
Land occupied by such tenants is properly cultivated at the expence of the proprietor as much as that occupied by slaves. There is, however, one very essential difference between them. Such tenants, being freemen, are capable of acquiring property, and having a certain proportion of the produce of the land, they have a plain interest that the whole produce should be as great as possible, in order that their own proportion may be so. A slave, on the contrary, who can acquire nothing but his maintenance, consults his own ease by making the land produce as little as possible over and above that maintenance. It is probable that it was partly upon account of this advantage, and partly upon account of the encroachments which the sovereign, always jealous of the great lords, gradually encouraged their villains to make upon their authority, and which seem at last to have been such as rendered this species of servitude altogether inconvenient, that tenure in villanage gradually wore out through the greater part of Europe. The time and manner, however, in which so important a revolution was brought about is one of the most obscure points in modern history. The Church of Rome claims great merit in it; and it is certain that so early as the twelfth century, Alexander III.*18 published a bull for the general emancipation of slaves. It seems, however, to have been rather a pious exhortation than a law to which exact obedience was required from the faithful. Slavery continued to take place almost universally for several centuries afterwards, till it was gradually abolished by the joint operation of the two interests above mentioned, that of the proprietor on the one hand, and that of the sovereign on the other. A villain enfranchised, and at the same time allowed to continue in possession of the land, having no stock of his own, could cultivate it only by means of what the landlord advanced to him, and must, therefore, have been what the French call a Metayer.
Wealth of nations, Book III, Chapter 2