Knox, William (1732–1810), government official and polemicist, was born at Clones, Co. Monaghan, son of Thomas Knox, physician, and Nicola Knox (née King). His father was a devout protestant, with strong Calvinist tendencies (he claimed descent from John Knox), and these religious principles became a rigid part of William's character from an early age. Educated locally, he may have entered TCD, but was soon involved in politics as a supporter of Sir Richard Cox (qv) (1702–66) during the political controversies of 1753–6. Deciding to seek his fortune abroad, in 1756 he was appointed provost marshal of the American colony of Georgia. There he built a large plantation worked by slaves, and served on the provincial council. Returning to London in 1762, he became an unofficial adviser to British ministers on imperial affairs. In 1765 he was dismissed as a colonial agent for Georgia because of his pamphlet The claim of the colonies, which defended the right of the British parliament to pass the controversial stamp act (1765), even though he questioned its efficacy.
Aligning himself with George Grenville (1712–70), who as prime minister (1763–5) had devised the stamp act, Knox became a leading pamphleteer and political adviser. His Present state of the nation (1768) is famous for outlining the theory of an imperial framework where both colony and home country worked in harmony for the greater good of the empire. As the work attacked the Rockingham whigs, it was answered by their chief polemicist, Edmund Burke (qv), in his Observations on a late state of the nation (1769). Knox's permanent search for financial security saw him accept office, and in 1770 he became under-secretary for the new American department. His pamphlets in defence of Lord North's administration widened the breach with the colonies, however. Always interested in Irish affairs, he pushed successfully for trade concessions (1778–80), even though he considered Ireland a colony. With the American war of independence he lost his Georgia plantation, and after the fall of the North ministry in 1782 was dismissed from office by a vengeful Rockingham government. Becoming a political adviser for hire, he was much in demand for his expertise on Anglo–American affairs. He frequently defended slavery on evangelical grounds, and argued that it allowed for the education and conversion of Africa. In 1790 he received compensation for the loss of his properties and decided to retire. He became a country farmer in England and Wales, but the lure of politics was frequently too great and he became an agent for the provinces of New Brunswick and Prince Edward Island as well as engaging in various public controversies. He urged a union between Britain and Ireland in the 1790s, but this was as much to threaten the Irish protestants into granting catholic rights as anything else. He died 25 August 1810 at Great Ealing, Middlesex.
He married (1756) Letitia Ford, from Ireland, who had a large fortune; they had seven children. His son Thomas was colonel in a volunteer regiment that Knox had founded in 1793, but was later dismissed.
Knox is widely regarded as one of the most influential imperialist thinkers of the eighteenth century. A brilliant, but egotistical man, whose political thinking was largely paternalistic, he helped develop, and later defended, the system of policies that led to the American revolution.