John Playfair
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John Playfair
FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and Literature, letters, judged to be "eminently distinguished in their subject". ...
, 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 Natural philosophy or philosophy of nature (from Latin ''philosophia naturalis'') is the philosophical study of physics, that is, nature and the physical universe, while ignoring any supernatural influence. It was dominant before the develop ...
at the
University of Edinburgh The University of Edinburgh (, ; abbreviated as ''Edin.'' in Post-nominal letters, post-nominals) is a Public university, public research university based in Edinburgh, Scotland. Founded by the City of Edinburgh Council, town council under th ...
. He is best known for his book ''Illustrations of the Huttonian Theory of the Earth'' (1802), which summarised the work of
James Hutton James Hutton (; 3 June Old Style and New Style dates, O.S. 1726 – 26 March 1797) was a Scottish geologist, Agricultural science, agriculturalist, chemist, chemical manufacturer, Natural history, naturalist and physician. Often referred to a ...
. It was through this book that Hutton's principle of
uniformitarianism Uniformitarianism, also known as the Doctrine of Uniformity or the Uniformitarian Principle, is the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in ...
, later taken up by
Charles Lyell Sir Charles Lyell, 1st Baronet, (14 November 1797 – 22 February 1875) was a Scottish geologist who demonstrated the power of known natural causes in explaining the earth's history. He is best known today for his association with Charles ...
, first reached a wide audience. Playfair's textbook ''Elements of Geometry'' made a brief expression of
Euclid Euclid (; ; BC) was an ancient Greek mathematician active as a geometer and logician. Considered the "father of geometry", he is chiefly known for the '' Elements'' treatise, which established the foundations of geometry that largely domina ...
's
parallel postulate In geometry, the parallel postulate is the fifth postulate in Euclid's ''Elements'' and a distinctive axiom in Euclidean geometry. It states that, in two-dimensional geometry: If a line segment intersects two straight lines forming two interior ...
known now as
Playfair's axiom In geometry, Playfair's axiom is an axiom that can be used instead of the fifth postulate of Euclid (the parallel postulate In geometry, the parallel postulate is the fifth postulate in Euclid's ''Elements'' and a distinctive axiom in Euclidea ...
. In 1783 he was a co-founder of the
Royal Society of Edinburgh The Royal Society of Edinburgh (RSE) is Scotland's national academy of science and letters. It is a registered charity that operates on a wholly independent and non-partisan basis and provides public benefit throughout Scotland. It was establis ...
. He served as General Secretary to the society 1798–1819.


Life

Born at Benvie, slightly west of
Dundee Dundee (; ; or , ) is the List of towns and cities in Scotland by population, fourth-largest city in Scotland. The mid-year population estimate for the locality was . It lies within the eastern central Lowlands on the north bank of the Firt ...
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 The University of St Andrews (, ; abbreviated as St And in post-nominals) is a public university in St Andrews, Scotland. It is the List of oldest universities in continuous operation, oldest of the four ancient universities of Scotland and, f ...
to study divinity. He also did further studies at
Edinburgh University The University of Edinburgh (, ; abbreviated as ''Edin.'' in post-nominals) is a public research university based in Edinburgh, Scotland. Founded by the town council under the authority of a royal charter from King James VI in 1582 and offi ...
. In 1766, when only 18, he was a candidate for the chair of mathematics in
Marischal College Marischal College ( ) is a large granite building on Broad Street in the centre of Aberdeen in north-east Scotland, and since 2011 has been the headquarters of Aberdeen City Council. The building was constructed for and is on long-term lease fr ...
(now part of the
University of Aberdeen The University of Aberdeen (abbreviated ''Aberd.'' in List of post-nominal letters (United Kingdom), post-nominals; ) is a public university, public research university in Aberdeen, Scotland. It was founded in 1495 when William Elphinstone, Bis ...
), and, although he was unsuccessful, his claims were admitted to be high. Six years later (1772) he applied for the chair of natural philosophy (physics) at St Andrews University, but again without success. In 1773 he was licensed to preach by the
Church of Scotland The Church of Scotland (CoS; ; ) is a Presbyterian denomination of Christianity that holds the status of the national church in Scotland. It is one of the country's largest, having 245,000 members in 2024 and 259,200 members in 2023. While mem ...
and was offered the united parishes of Liff and his home parish of Benvie (made vacant by the death of his father). However, Playfair chose to continue his studies in mathematics and physics, and in 1782 he resigned his charge to become the tutor of
Adam Ferguson Adam Ferguson, (Scottish Gaelic: ''Adhamh MacFhearghais''), also known as Ferguson of Raith (1 July N.S. /20 June O.S. 1723 – 22 February 1816), was a Scottish philosopher and historian of the Scottish Enlightenment. Ferguson was sympath ...
. By this arrangement Playfair regularly visited
Edinburgh Edinburgh is the capital city of Scotland and one of its 32 Council areas of Scotland, council areas. The city is located in southeast Scotland and is bounded to the north by the Firth of Forth and to the south by the Pentland Hills. Edinburgh ...
and went on to cultivate the
literary Literature is any collection of written work, but it is also used more narrowly for writings specifically considered to be an art form, especially novels, plays, and poems. It includes both print and digital writing. In recent centuries, ...
and scientific society for which the city was at that time specially distinguished. In particular, he attended the natural history course of John Walker. Through
Nevil Maskelyne Nevil Maskelyne (; 6 October 1732 – 9 February 1811) was the fifth British Astronomer Royal. He held the office from 1765 to 1811. He was the first person to scientifically measure the mass of the planet Earth. He created '' The Nautical Al ...
, whose acquaintance he had first made in the course of the celebrated
Schiehallion experiment The Schiehallion experiment was an 18th-century experiment to determine the Arithmetic mean, mean density of the Earth. Funded by a grant from the Royal Society, it was conducted in the summer of 1774 around the Scottish Mountains and hills of S ...
s in 1774, he also gained access to the scientific circles of
London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
. In 1785 when
Dugald Stewart Dugald Stewart (; 22 November 175311 June 1828) was a Scottish philosopher and mathematician. Today regarded as one of the most important figures of the later Scottish Enlightenment, he was renowned as a populariser of the work of Francis Hutc ...
succeeded Ferguson in the University of Edinburgh Chair of Moral Philosophy, Playfair succeeded the former to become the chair of mathematics. In 1795 Playfair published an alternative, more stringent formulation of Euclid's parallel postulate, which is now called
Playfair's axiom In geometry, Playfair's axiom is an axiom that can be used instead of the fifth postulate of Euclid (the parallel postulate In geometry, the parallel postulate is the fifth postulate in Euclid's ''Elements'' and a distinctive axiom in Euclidea ...
. Although the axiom bears Playfair's name, he did not create it, but credited others, in particular William Ludlam with its prior use. In 1802 Playfair published his celebrated volume entitled ''Illustrations of the Huttonian Theory of the Earth.'' The influence exerted by
James Hutton James Hutton (; 3 June Old Style and New Style dates, O.S. 1726 – 26 March 1797) was a Scottish geologist, Agricultural science, agriculturalist, chemist, chemical manufacturer, Natural history, naturalist and physician. Often referred to a ...
on the development of geology is thought to be largely due to its publication. In 1805 Playfair exchanged the Chair of Mathematics for that of natural philosophy in succession to John Robison, whom also he succeeded as general secretary to the
Royal Society of Edinburgh The Royal Society of Edinburgh (RSE) is Scotland's national academy of science and letters. It is a registered charity that operates on a wholly independent and non-partisan basis and provides public benefit throughout Scotland. It was establis ...
. He took a prominent part, on the liberal side, in the
ecclesiastical {{Short pages monitor