It was on January 31st 1865, 154 years ago today, that the US Congress passed the 13th Amendment that banned slavery, and sent it out to the states for ratification. Nearly two years earlier, Lincoln had used Presidential war powers to free slaves in Confederate states as they came under Union control, but the amendment made slavery unconstitutional.

It was one landmark among several that made illegal the ownership of one human being by another, the total denial of liberty. It predates written records and was practised in many cultures. Slavery involved suffering, and many captured slaves died in transit. The Arab slave trade, for example, which lasted over 1,000 years, typically saw 6 or even 10 die for every one that reached the destination. In the Atlantic slave ships, some 15 percent died en route, while the remainder suffered appalling conditions.

Other landmarks in the campaign for its abolition included the 1807 UK Act, inspired by Wilberforce, that abolished the slave trade throughout the British Empire. In the half-century following, the British navy seized approximately 1,600 slave ships and freed 150,000 Africans who were aboard. Wilberforce himself lived to see the 1835 Slavery Abolition Act pass into law.

A US landmark was the 1807 Act under Jefferson that banned the import of slaves, although it left the domestic practice in place. By the civil war it was estimated that one-third of Southern families owned slaves, so the 13th Amendment made a vast difference to the lives of millions.

The 1948 Declaration of Human Rights specified that, "No one shall be held in slavery or servitude; slavery and the slave trade shall be prohibited in all their forms." No person today may legally be enslaved or held in slavery, and the most basic human freedom to live free from bondage is enshrined in international law. To those who say slavery is still with us in the form of human trafficking, chattel slavery, forced marriage and child soldiers, Steven Pinker gives an eloquent distinction between what it is now, and what it was for most of human history:

“There is an enormous difference between a clandestine, illegal, and universally decried practice in a few parts of the world and an open, institutionalized, and universally approved practice everywhere in the world."