When and how did people begin to consider slavery immoral?

Question

Consider this: In the ancient world, murder and theft were prohibited. However, slavery was ubiquitous and considered normal. AFAIK, nobody thought of it as immoral, though probably some called for kind treatment of slaves.

So when did people start talking of the very institution of slavery as immoral and demanding its abolition? And how did they justify that? Obviously, since they had to convince others of their point of view, they couldn't just say "We hold this truth to be self-evident".

I know that the Church prohibited slavery in the early centuries of its existence (but then allowed owning non-Christian slaves).

Answer 1

As @Luke states, there seems to have been a tipping point in the 19th century; I'd have dated it a few years earlier, and I'd have located it in England; Britain started out as a major participant in the slave trade (more slaves went to British possessions in the Caribbean than to the US colonies). Sometime between 1780's and 1830's there was a major shift in perception and values. I would point to the Quaker AntiSlavery committees and William Wilberforce as representatives of that shift.

The British campaign to abolish the slave trade is generally considered to have begun in the 1780s with the establishment of the Quakers' antislavery committees, and their presentation to Parliament of the first slave trade petition in 1783.[53][54] The same year, Wilberforce, while dining with his old Cambridge friend Gerard Edwards,[55] met Rev. James Ramsay, a ship's surgeon who had become a clergyman on the island of St Christopher (later St Kitts) in the Leeward Islands, and a medical supervisor of the plantations there. What Ramsay had witnessed of the conditions endured by the slaves, both at sea and on the plantations, horrified him. Returning to England after fifteen years, he accepted the living of Teston, Kent in 1781, and there met Sir Charles Middleton, Lady Middleton, Thomas Clarkson, Hannah More and others, a group that later became known as the Testonites.[56] Interested in promoting Christianity and moral improvement in Britain and overseas, they were appalled by Ramsay's reports of the depraved lifestyles of slave owners, the cruel treatment meted out to the enslaved, and the lack of Christian instruction provided to the slaves.[57] With their encouragement and help, Ramsay spent three years writing An essay on the treatment and conversion of African slaves in the British sugar colonies, which was highly critical of slavery in the West Indies. The book, published in 1784, was to have an important impact in raising public awareness and interest, and it excited the ire of West Indian planters who in the coming years attacked both Ramsay and his ideas in a series of pro-slavery tracts. Wikipedia summary of William Wilberforce

The question is far larger; books could and have been written on the subject, but I hope this pointer is useful in setting up further research.

Answer 2

It is incorrect to perceive that there was a single concept of slavery in ancient world. The Latin word for slave, "servus" at the same time meant a servant.

The concept of slavery differed very much between ancient societies and also differed in time. Sometimes a slave would be considered a member of the family to the extent that a formal kinly relationship such as formal adoption would be required for having a slave while in other societies the concept of slavery rose from the captured enemies or even possibly, rebels. Still in others one could become a slave for failing to pay a debt and could earn freedom back upon paying the sum or serving a certain term.

The societies differed much in the social status of "slaves" and their rights and the very word for slave could only barely be translated from one language to another without loosing a part of the meaning.

We currently apply the same term "slave" to penal farm convicts, prisoners of war, debtors forced to work to repay debts, dependent peasants, minor clan members and so on, who all had different legal status.

The situation is quite similar to how we apply the term "king" to various ancient titles that had little in common (rex, basilios, vanax, archon, archagestes, despotes, hegemon, tyrannos etc). There was little in common between elected and not heriditary Roman rex responsive to the senate and a Egyptian pharaon yet we call the both "kings". If a Roman of the time appeared in modern day he would possibly call the president "rex" and the penal farm prisoners "public slaves".

Answer 3

Wikipedia states:

Essenes
Slave ownership was widely accepted by the majority of early Jewish societies, but the Essenes were a small, ascetic sect that reportedly renounced slavery,[16] although some scholars question whether the Essenes actually renounced slavery.[17][18]

The sources for those references is Hezser, Catherine, "Jewish slavery in antiquity", Oxford University Press, 2005

Please note that due to economic considerations, non-slavery society was not a very viable proposition in ancient times.

Answer 4

As Mark C. Wallace very correctly points out, the British antislavery movement of the 18th and 19th centuries was the first serious anti-slavery movement that managed to roll back slavery. However, no discussion of anti-slavery can be complete without a mention of the good friar Las Casas.