Thomas, an eminent physician and moralist, was born at Warrington in Lancashire in 1740. His characteristic enthusiasm began to appear at an early age. After studying with great ardour at the newly-instituted academy of his native place, he devoted himself to the medical profession. He began his studies at Edinburgh in 1761, continued them at London in 1764, and finished them by graduating at Leyden in 1765. But it was not until 1767, when Percival commenced to practise as a physician in Manchester, that his enthusiasm obtained its full scope. Fond of his profession, addicted to scientific investigations and discussions, earnest, and religious, he now entered upon a career of wide and varied activity. He became a frequent contributor to the Philosophical Transactions of London; and he became the chief instrument in establishing the Literary and Philosophical Society of Manchester. His numerous papers on medical subjects were devoted to the cause of public health; and his Moral Dissertations, Instructions to Children, and Medical Ethics were consecrated to the interests of public morality. His professional duties were also discharged with the most conscientious assiduity till his death in August 1804. The entire works of Dr. Percival, accompanied with a Life, were published by his son, in 4 vols. 8vo, London, 1807.