Wilson identifies him with the John Alexander who was a pupil of Isaac Noble and Congregationalist minister at Gloucester 1712–18.
He afterwards moved to Dublin, where he was installed minister of Plunket Street Presbyterian congregation on 15 November 1730.
He was moderator of the General Synod of Ulster, 1734, and died in Dublin on 1 November 1743 and was buried there.
He was a linguist and patristic scholar; he published The Primitive Doctrine of Christ's Divinity … in an Essay on Irenæus … 1727.
He left two daughters Mary (1734), Hannah (1742) and two sons, John and Benjamin (1737–1768): the latter, was a doctor of medicine, and translated J.