John Playfair FRSE, FRS (10 March 1748 – 20 July 1819) was a Church of Scotland minister, remembered as a scientist and mathematician, and a professor of natural philosophy at the University of Edinburgh. He is best known for his book Illustrations of the Huttonian Theory of the Earth (1802), which summarised the work of James Hutton. It was through this book that Hutton's principle of uniformitarianism, later taken up by Charles Lyell, first reached a wide audience. Playfair's textbook Elements of Geometry made a brief expression of Euclid's parallel postulate known now as Playfair's axiom.
In 1783 he was a co-founder of the Royal Society of Edinburgh. He served as General Secretary to the society 1798–1819.
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Life
Born at Benvie, slightly west of Dundee to Margaret Young (1719/20 – 1805) and Reverend James Playfair (died 1772), the kirk minister of Liff and Benvie.
Playfair was educated at home until the age of 14, when he entered the University of St Andrews to study divinity. He also did further studies at Edinburgh University. In 1766, when only 18, he was a candidate for the chair of mathematics in Marischal College (now part of the University of Aberdeen), and, although he was unsuccessful, his claims were admitted to be high.