William Molyneux FRS (; 17 April 1656 – 11 October 1698) was an Anglo-Irish writer on science, politics and natural philosophy.
He is noted as a close friend of fellow philosopher John Locke, and for proposing Molyneux's Problem, a thought experiment widely discussed.
Life
He was born in Dublin to Samuel Molyneux (1616–1693), lawyer, landowner and Master Gunner for Ireland, (whose grandfather, Sir Thomas Molyneux, had come to Dublin from Calais in the 1560s), and his wife, Anne, née Dowdall. The second of five children, William Molyneux came from a relatively prosperous Anglican background, with his father established at Castle Dillon in County Armagh, and his uncle Colonel Adam Molyneux holding large estates inherited from the Dowdall's in Ballymulvey, near Ballymahon in County Longford. He was close to his brother Sir Thomas Molyneux, with whom he later shared philosophical interests. His sister Jane married Anthony Dopping, the eventual Anglican Bishop of Meath. In 1671 Molyneux started at Trinity College Dublin where he became an avid reader of the leading figures of the Scientific Revolution. After attaining a Bachelor of Arts there, Molyneux was sent to study law in the Middle Temple, London from 1675 to 1678. In 1678 he married Lucy Domville (?–1691), the youngest daughter of Sir Wiliam Domville, the Attorney-General for Ireland, and his wife Bridget Lake. His wife became ill, which led to blindness after their marriage, and died young. Of their 3 children, only Samuel Molyneux (1689–1728) lived past childhood. Samuel went on to become an astronomer and politician who worked with his father on various scientific endeavours.
Career and publications
Because of his inheritance, Molyneux was financially independent. Nonetheless, he held a number of official positions throughout his life. He was appointed Joint Surveyor General of the King's buildings and works in Ireland in 1684, serving alongside William Robinson. In 1687 he invented a new type of sundial called a Sciothericum telescopicum that used a special double gnomon and a telescope to measure the time of noon to within 15 seconds. He represented Dublin University in Parliament from 1692 until his death. He had also served as a commissioner of forfeited estates in 1693, resigning a few months later due to ill health.
Meanwhile, Molyneux was responsible for a number of publications reflecting his diverse interests. His first book was editing and translating into English the work of René Descartes which was published in London, 1680 as Six Metaphysical Meditations, Wherein it is Proved that there is a God.... In 1682 Molyneux collaborated with Roderic O'Flaherty to collect material for Moses Pitt's Atlas. In 1685, Pitt's financial crisis lead to cancellation of the project but much valuable early Irish history had been collected. Molyneux struck a friendship with O'Flaherty and assisted when the latter's treatise Ogygia was published in London.
Meanwhile, in October 1683 he founded the Dublin Philosophical Society along the lines of the Royal Society (of which Molyneux became a fellow in 1685), and became its first Secretary. He was active in the proceedings of the society—recording weather data, calculating eclipses and demonstrating instruments and experiments.
Molyneux also published several papers in Philosophical Transactions, as well as papers on optics, natural philosophy, and miscellaneous topics. Perhaps his best known scientific work was Dioptrica Nova, A treatise of dioptricks in two parts, wherein the various effects and appearances of spherick glasses, both convex and concave, single and combined, in telescopes and microscopes, together with their usefulness in many concerns of humane life, are explained, published in London 1692.
After John Locke published his Essay Concerning Human Understanding (1690), Molyneux wrote to him praising the work.
