The abolition (ending) of slavery marked an important moment in world history, especially in the Atlantic. In 1800, plantations worked by enslaved people, particularly Africans, stretched across the Americas. Tens of thousands of enslaved people were taken every year from Africa to the Americas in the most horrendous conditions. Their initial capture and journey across the Atlantic posed so many dangers that many died before leaving the boat. Those who survived suffered a life of harsh labor, terrible living conditions, and an almost complete lack of rights. Slavery existed elsewhere in the world, particularly in South Asia and the Islamic World, but nowhere was it as deep-rooted as in the Americas.

Beginning in 1803, slavery and the slave trade were outlawed in many parts of the world. In 1807-1808, both the United States and Britain outlawed the slave trade, making it illegal to bring enslaved people into their territory. (But they kept slavery legal and continued to enslave the people they had already imported, as well as their descendants.) Independent Haiti became the first country in the Americas to abolish slavery in 1804, followed by Cuba in 1886, Mexico in 1829, and much of Latin America soon after. The United States would not follow suit until after the Civil War ended in 1865. Meanwhile, the major European slave-trading powers slowly abolished the trade. The Netherlands did so in 1814, followed by Portugal, Spain, and France by 1820.

Enslaved people were still smuggled illegally into the Americas, in particular to Cuba and Brazil. In these places, slavery remained legal until quite late in the nineteenth century. The tide against slavery had definitely turned, however, and slavery would be outlawed in many other regions of the world in the years that followed.

Why did abolition just “happen” in the nineteenth century? What shifted in this era that caused some of the biggest slave-owning and slave-trading societies to suddenly become abolitionists? There are at least three important theories to consider.

Theory 1: Free labor and free wages

Perhaps the most dramatic shift toward abolitionism occurred in Britain and parts of English-speaking North America. In the 1790s, Britain had the world’s largest slave-trading industry, but in 1807, it became the first large country to criminalize the slave trade. Slavery was later abolished throughout the British Empire and in English-speaking northern U.S. states and parts of Canada. In 1827, for example, New York passed a law abolishing slavery in that state. What changed in these regions?

One theory is that it was economic. There was an emerging middle class of business owners who paid their workers and saw slavery as unfairly competing with their businesses. Their only participation was that they had occasionally invested in slave-trading voyages, but profits were dropping in that terrible industry. Instead, they invested in businesses and paid their workers. Furthermore, many businesspeople wished to participate in trade in Africa, either by buying resources or by selling finished goods to African buyers. The slave trade created chaos in Africa, which made it more difficult and less profitable to do business there. Ending the slave trade, they hoped, could make business in Africa more stable and profitable.

Furthermore, these businesspeople were often competing for political power with an upper class of land-owning nobles who were likely to have slave plantations. Ending slavery would hurt these political rivals and help level the playing field.

Thus, as historian (and later prime minister of Trinidad and Tobago) Eric Williams argues, it can be argued that slavery was abolished only when it made economic sense for some people.

Theory 2: Morality

Not everyone agrees that money and economic motives were at the heart of abolitionism. Philosopher John Stuart Mill, who lived in this period, argued that abolition was not the result of economic reasons. He said it was caused “by the spread of moral convictions.” Mill wrote: “It is what men think that determines how they act.”

These changing ideas might have been related to Enlightenment thinking. The Enlightenment, which began in the late eighteenth century, promoted ideals of individual freedom. These ideals included “free labor,” meaning that people were paid wages for their work rather than enslaved. Enlightenment thinkers also debated who was human and developed ideas about the brotherhood of men. These discussions inspired many leaders of the French Revolution and got people talking about the morality of slavery. But there were limits to this brotherhood. In general, the new morality did not see enslaved black people as equals. These Enlightenment ideas were partly a result of new ways to interpret the Bible. Slavery had often been defended through readings of Old Testament texts that seemed to justify enslavement, especially of Africans. Some abolitionists were humanists (those who believed strongly in the worth of individual humans) who rejected these texts entirely. But most of the leaders of the movement—especially in Britain—were actually evangelical Christians who found new freedoms to reread these texts. Noting that the gospel called for “goodwill towards all men,” they argued that slavery went against the spirit of Christianity.

We can’t forget that many of these same evangelical abolitionists were also businessmen who stood to profit from the abolition of slavery. However, in the 1790s, working-class people in Britain and other locations began to support the abolition of the slave trade, even though they knew it wouldn’t really affect the working class financially. They were motivated by a belief that the slave trade was evil, and that supporting abolition was the moral and ethical thing to do. Their main weapon was a boycott of sugar and rum, two products produced overwhelmingly by enslaved people. This was pretty hard for many workers, but working-class families around Britain stopped using sugar in 1792 in support of a ban on the Atlantic slave trade. They did it again in the 1820s during the campaign to abolish slavery across the empire. These families had little reason to boycott two of their favorite products, except for moral issues. For some it was probably true morality; for others, it might have been a more self-serving wish to make others see them as moral.

Theory 3: The actions of Africans in the Americas and Europe

Another theory argues that black Americans and Europeans, many of them formerly enslaved or the descendants of enslaved people, took actions that led to the end of slavery.

In Britain, some of the most effective abolitionists were black. One example was Olaudah Equiano, a formerly enslaved man who argued that that slavery conflicted with Christian belief. His book was one of the most powerful abolitionist texts of the day, and he spoke against slavery all across Britain. Another free African, Ottobah Cugoano, also played an important role and called for the abolition of slavery in his autobiography.

Black abolitionists played an even greater role in France and its empire. During the French Revolution, black Frenchmen and Frenchwomen called for an end to slavery. They included Jeanne Odo, a woman who was born in the vast plantation colony of Saint- Domingue (now called Haiti). Another figure was Jean- Baptiste Belley, a Senegalese man who had been sold into slavery in Saint-Domingue. Odo, Belley, and others tried to get the French constitution to outlaw slavery. But the most significant actions took place during the Haitian Revolution in the French Caribbean colony of Saint-Domingue. Enslaved people rebelled against the French colonists, fought off the French army, and gained their freedom in 1804. They forcibly ended slavery in France’s largest slave colony and forced France to reconsider slavery elsewhere.

France would abolish slavery in all its colonies by 1848.

In Mexico, in the 1820s, abolitionism was also led by people of African descent. Abolition was eventually declared for almost all of Mexico in 1829, by Vicente Guerrero, a president of partly African ancestry. The United States, however, wouldn’t abolish slavery nationally for three and a half decades.

Conclusion

Gradually, most of the world’s nation-states abolished slavery by the beginning of the twentieth century, barely more than 100 years ago. Forms of slavery remained (and still remain today) in many places, however. For example, in many parts of the Islamic World, slavery continued to operate outside the rule of law. In South Asia, class systems kept people in terrible conditions, forcing them to perform harsh labor with no real escape. In the United States and many parts of the Americas, racist laws continued to oppress many of the formerly enslaved. Many black Americans were forced into sharecropping, which amounted to slave labor.