Granville Sharp was one of the first British campaigners for the abolition of slavery. His involvement with the cause began following his efforts to secure the freedom of Jonathan Strong, a young Black man who had been badly beaten and left for dead by his enslaver, David Lisle in 1765. Granville and his brother William rescued Strong and tended to his wounds, looking after him for four months, after which they gained him employment as a runner for an apothecary. In 1767, Lisle saw Strong running errands and arranged for his capture, intending to sell him to James Kerr, an enslaver in Jamaica. Lisle argued that Strong was still his property and sold the young man to Kerr for £30. Strong got word to Sharp, who defended him in court against Kerr. Eventually the case was dismissed, Kerr ordered to pay substantial damages, and Strong was granted his freedom.

Jonathan Strong died five years later at the age of 25, but Sharp continued to advocate for the rights of Black people until his death in 1813. This book, published in 1769, was the first treatise in England to explicitly attack the concept of slavery, arguing that the laws of nature made all humans equal regardless of any artificial laws imposed by society and that no monetary value could be applied to a human life.
It was an influential work, gaining Sharp many followers among those that had long questioned the morality of enslaving other people. In 1787, following a series of high profile cases involving the maltreatment of enslaved people, Sharp and his fellow abolitionists established the Society for Effecting the Abolition of the Slave Trade to further the cause. The slave trade was abolished in Britain in 1807, with the abolition of slavery across the British Empire being achieved in 1834.