He was the son of Robert Flint, at that time a farm overseer, and his wife, Grace Paterson. His first school was at Moffat. In 1852, he entered Glasgow University, where he distinguished himself (without graduating) in arts and divinity. Having been employed as a lay missionary by the 'Elders' Association' of Glasgow, he was licensed to preach in 1858, and for a short time acted as assistant to Norman Macleod (1812-1872), at the Barony Church, Glasgow. He was minister of the East Church, Aberdeen (1859-62) and of Kilconquhar, Fife (1862-4), a country parish, which gave him leisure for study, improved by visits to Germany