He was born in Edinburgh in 1708, the son of Rev James Webster, a covenanting minister originally from Fife. Alexander became a minister of the Church of Scotland, beginning his career in Culross in Fife. There he met and married Mary Erskine of Alva, for whom he wrote: He propounded a scheme in 1742 for providing pensions for the widows of ministers. The tables which he drew up from information obtained from all the presbyteries of Scotland were based on a system of actuarial calculation that supplied a precedent followed by insurance companies in modern times for reckoning averages of longevity. Webster published in 1748 his Calculations, setting forth the principles on which his scheme for widows' pensions was based; he also wrote a defence of the Methodist movement in 1742, and Zeal for the Civil and Religious Interests of Mankind Commended. In 1755 the government commissioned Webster to obtain data for the first census of Scotland, which he carried out in the same year. In 1753 he was elected moderator of the General Assembly; in 1771 he was appointed a dean of the Chapel Royal and chaplain to George III in Scotland. In 1775 he is listed as living on Castlehill, at the top of the Royal Mile. Socially, despite his 'High Flying' Evangelical position in the Kirk, he was a convivial man, known as Bonum Magnum for his capacity for claret. His wife's nephew Boswell often mentions dining with the family. He is buried beside Mary in Greyfriars Kirkyard, Edinburgh, in a now-unmarked grave.
Family
He was married to Mary Erskine.They had several children. His two eldest sons, John and James, served in the American Revolutionary War. John was a Captain in the 4th Regiment of Foot. James was especially well regarded as Lieutenant-Colonel of the 33rd Foot, Lord Cornwallis's own regiment, and acting Brigadier. When he died of wounds after the battle of Guilford Courthouse in 1781, Cornwallis wrote a touching letter of condolence to Alexander Webster. Mary's sister Euphemia Erskine, was the mother ofJames Boswell.
