“To [the Marquis de] Sade, of course, it had all been folly. There was no brotherhood of man; there was no duty owed by the weak to the strong. Evangelicals, like Jacobins, were the dupes of their shared inheritance: their belief in progress; their conviction in the potential of reform; their faith in humanity might be brought to light. Yet it was precisely this kinship, this synergy, that enabled Castlereagh, faced by the obduracy of his fellow foreign ministers, to craft a compromise that was, in every sense of the word, enlightened. Unable to force through an explicit outlawing of the slave trade, he settled instead for something at once more nebulous and more far-reaching. On 8 February 1815, eight powers in Europe signed up to a momentous declaration. Slavery, it stated, was ‘repugnant to the principles of humanity and universal morality’. The language of evangelical Protestantism was fused with that of the French Revolution. Napoleon, slipping his place of exile three weeks after the declaration had been signed, and looking to rally international support for his return, had no hesitation in proclaiming his support for the declaration. That June, in the great battle outside Brussels that terminally ended his ambitions, both sides were agreed that slavery, as an institution, was an abomination. The twin traditions of Britain and France, of Benjamin Lay and Voltaire, of enthusiasts for the Spirit and enthusiasts for reason, had joined in amity even before the first cannon was fired at Waterloo. The irony was one that neither Protestants nor atheists cared to dwell upon: that an age of enlightenment and revolution had served to establish as international law a principle that derived from the depths of the Catholic past. Increasingly, it was in the language of human rights that Europe would proclaim its values to the world.”
Tom Holland Dominion: How the Christian Revolution Remade the World