Thomas Percival was one of the most significant figures in Manchester medical history. He was born at Warrington in 1740, and following the death of his parents, was brought up by his eldest sister. He studied at Warrington grammar school, before training to become a doctor. A dissenter, Percival was educated at the newly-established Warrington Academy, which provided a more advanced education for those barred from attending the English universities. He then studied at Edinburgh University, where he was befriended by the philosopher David Hume. He also spent time in London, where he was elected a FRS. After completing his studies at Edinburgh he moved to Leyden University, where he took his medical degree in 1765, He returned to practise medicine in Warrington but in 1767 moved to Manchester, where he was to spend the rest of his life.
In 1778 he was elected physician at the Manchester Infirmary but stood down from this post in 1780. He was Physician Extraordinary at the Infirmary from 1782-1804. Percival involved himself with public health matters, he was involved in the Manchester Board of Health, and was an advocate of factory legislation. He was interested in medical statistics and in 1770 produced proposals for better recording of baptisms, marriages and burials, with tables for the sex and ages of those recorded and a list of the diseases from which people died and the number dying of each disease by age, and season of the year. Percival argued that these statistics would provide valuable data on the impact of climate and occupation on disease and the relative frequency of each disease.
Percival was also very active in the intellectual and cultural life of Manchester; it was at his house that the Manchester Literary and Philosophical Society was set up in 1781. He was its first president. In 1785 Percival helped with the transfer of the Warrington Academy to Manchester.
Percival published widely on medical, scientific and philosophical subjects. He produced two volumes of Essays, medical, philosophical and experimental (1967-1773),Moral tales, fables and reflections, a series of short tales to promote virtue and knowledge among the young, and this work was translated into French and German. Percival is however best known for his work on medical ethics. He had a long-standing interest in the conduct of hospital care and in 1792 he composed at the request of the Infirmary, "A scheme of professional conduct relative to hospitals and other medical charities". Percival then expanded this scheme into a general system of medical ethics, which was published as Medical Ethics in 1803 (a privately printed version had been distributed to friends in 1794) A second edition of the Ethics was published in 1827 and a third edition in 1849. The code of ethics of the American Medical Association was based on Percival's work.
Percival died on 30 August 1804, and was buried in the parish church of Warrington.