[1] After four years' schooling, Kinghorn was taken on trial as apprentice to watch- and clock-making at Hull in 1779, but in March 1781 became a clerk in the white-lead works at Elswick, Northumberland of Walker Fishwick & Co.[1][2] On 20 April 1783 he was baptised by his father at Burton-Bishop, and considered entering the ministry.

He made the acquaintance of Robert Hall, and had thoughts of joining him at the University of Aberdeen, but on 20 August 1784 he entered Bristol Baptist Academy, under Caleb Evans.

At Bristol, Kinghorn developed friendships with James Hinton (1761–1823), Anthony Robinson (Unitarian) (1762–1827, his roommate), and Samuel Pearce.

[4] From 1790 Kinghorn was a member of the Norwich Speculative Society, entering the intellectual life of the city, of which William Taylor was the effective leader.

[5] In 1804 Kinghorn was invited to become head of the Northern Baptist Academy, then being set up in Bradford, but he preferred pastoral work.

In a controversy with Robert Hall, which began in 1816, Kinghorn took the side of close communion, requiring adult baptism a condition of participation in the Lord's Supper.