The Torah permits slavery ( Leviticus 25:44). On the other hand, Proverbs 3:17 states, in reference to wisdom, “Her ways are ways of pleasantness, and all her paths are peace.” In that case, how can the Torah, the embodiment of divine wisdom, condone the evil of slavery?
I believe the answer is that slavery is not essentially evil.
Generally slavery occurs under certain specific conditions. First of all, there must be a high demand for unskilled labor. Second of all, there must be a large community of primitive people available who can be forced, with minimal supervision, to do that labor.
In ancient Rome, slaves were often German barbarians. In medieval Europe Slavs were often enslaved and the English word “slave” comes from them. In modern times, Europeans enslaved black Africans. I believe that generally, slaves were far more primitive technologically than their masters since otherwise it would be difficult to capture them and perhaps even more difficult to make them work without payment. Educated people tend to find ways to malinger, escape or revolt. They will only work under heavy guard, which is expensive and therefore negates the benefit of using slaves. (This probably was the real reason closing the Soviet labor camps in the 1950’s.)
Therefore, we see that slavery tended to introduce primitive people to more advanced societies and thereby to spread civilization. Seemingly, slavery is similar to colonialism and it often existed in connection with colonialism. Colonialism could be brutal, however it could be benign as well. The same may be true of slavery. I would not say that slave traders and slave owners were exactly Peace Corp volunteers, however that may not be so far from the truth.
Witness the results of slavery in modern times. Although I do not condone the unneeded cruelty of some American slave owners, and neither does Judaism, however if not for slavery, millions of blacks would not be enjoying a comfortable life in America. People like the Reverend Jeremiah Wright may be filled with hatred for white Americans, however perhaps they should have a little gratitude also. What type life style do their never enslaved cousins in Africa have? The life expectancy of blacks in America is 73 years, for blacks in Africa it's 46 years.
Within Judaism, slavery meant that the slave had a semi-Jewish status (he would be circumcised if male, observe the Sabbath, but not attend synagogue) and and upon being freed, which inevitably happened eventually to the slave or his descendants, he became a full-fledged Jew. There can be little doubt that the ancestors of many modern Jews were at one time slaves owned by Jews. Slavery therefore was a means to spiritually enlighten primitive gentiles. Apparently because of this, the Catholic Church fought repeatedly against the Jewish ownership of gentile slaves.