The quiet minister whose famous theorem only appeared after he died
Thomas Bayes spent years as a Presbyterian minister in Tunbridge Wells and never published the idea that made him famous. After his death in 1761, his friend Richard Price found his notes on probability and presented them to the Royal Society. Today Bayesian thinking underpins machine learning, risk assessment and robot mapping.
Bayes was the son of a London Presbyterian minister, from a prominent nonconformist family with Sheffield roots. He studied logic and theology at the University of Edinburgh from 1719, helped at his father's London chapel, and around 1734 moved to Kent to lead the Mount Sion Chapel in Tunbridge Wells, where he stayed until 1752.
In his lifetime he published just two known works. One was a theological argument that the chief purpose of divine providence is the happiness of its creatures. The other, issued anonymously in 1736, defended Isaac Newton's calculus against the philosopher-bishop George Berkeley's attack on its logical foundations. That defence is thought to be what won him election to the Royal Society in 1742.
Later he turned to probability, perhaps prompted by a 1755 work of Thomas Simpson, by the writings of Abraham de Moivre, or, some suggest, by a wish to answer David Hume's argument against believing reports of miracles. His essay tackled what was then called inverse probability: rather than asking how likely a black ball is from an urn of known contents, asking what the balls already drawn reveal about what is inside. Price read the essay to the Royal Society in 1763 and saw it into print the following year.
Bayes might not have recognised the broad philosophy that now bears his name, which treats probability as strength of belief and was largely developed by Pierre-Simon Laplace. The label Bayesian has been used in that sense only since about 1950, and cheap computing then made the methods practical across many sciences. He was buried in Bunhill Fields in London, where many nonconformists lie. Edinburgh opened a £45 million research centre named after him in 2018, and in 2021 Cass Business School, on nearby Bunhill Row, announced it would take his name.
Source: Thomas Bayes
