Flint was born at Greenburn, Sibbaldbie near Applegarth in Dumfriesshire on 14 March 1838,[1] the son of Grace Johnston (née Paterson) and Robert Flint, a farm overseer.[2] His first school was at Evan Water then he moved to Moffat.[3] In 1852, he entered the University of Glasgow where he distinguished himself (without graduating) in arts and divinity.[4]
Having been employed as a lay missionary by the 'El ders' Association of Glasgow', Flint was licensed to preach as a Church of Scotland minister by the Presbytery of Glasgow in June 1858, and for a short time acted as assistant to Norman Macleod, at the Barony Church, Glasgow. He was minister of the East Church, Aberdeen from 1859 to 1862, and of Kilconquhar church in Fife from 1862 to 1864, a small country village parish, which gave him leisure for study, improved by visits to Germany.[4]
On the death of James Frederick Ferrier in 1864, Flint was elected to succeed him in the moral philosophy chair at the University of St Andrews, among the competing candidates being Thomas Hill Green. This chair he held till 1876, when he succeeded Thomas Jackson Crawford in the divinity chair of the University of Edinburgh. On this appointment he was awarded doctorates by both the University of Glasgow (LLD) and the University of Edinburgh (DD). Thomas Chalmers had similarly migrated from the one chair to the other.[4]
Flint died, unmarried, at his residence, 5 Royal Terrace, Edinburgh, on 25 November 1910.[4] In 2015 the building was occupied by a restaurant and hotel.[6]