Slaves were either criminals who had been convicted for serious crimes, or prisoners taken in battle, or foreigners who subjected themselves willingly to slavery in Utopia because they were under the death penalty in their own country or because of a life of unendurable poverty and drudgery in their homeland. According to the Utopian system of servitude, allowance was provided for a slave to gain his freedom by good behavior and clear evidence of reformation of character. Furthermore, slavery was not hereditary; hence, the children of slaves were granted free citizen status.
The practice of slavery among the Utopians is regarded by many modern readers as the most damaging feature of an otherwise idealistic scheme of society. In passing judgment, however, it is well to view the situation in its historic perspective. Not only was slavery an accepted institution among the Greeks and Romans and even incorporated into Plato's ideal Republic, it was also accepted among European nations in More's time, with the proviso that it was not considered proper to make slaves of Christian captives. Actually, the movement among Christian nations to abolish slavery did not develop in strength until the nineteenth century.
It is also to be noted that the treatment of slaves in Utopia was, in some respects, humane. Hythloday's justification of the practice, if we may judge from his discussion of the penal code in Book I, would have been that it is far better to sentence criminals to performing useful labor for the state than to hang them.