In 1859, Charles Darwin published The Origin of Species, and in the same year, at the age of twenty-five, Robert Flint became minister of the East Church in Aberdeen. He was a very reserved and serious young man, unsure of himself on social occasions, preferring the company of his parents and sister who stayed with him in his various homes. Flint took immense care in the preparation of his sermons, revising them almost until it was time to enter the pulpit. In his first winter as a parish minister he preached a series of sermons on the parables about the Kingdom of God recorded in Matthew's Gospel Chapter 13. He repeated them two years later when he became minister of Kilconquhar in the East Neuk of Fife, and they were published in 1865, when he became Professor of Moral Philosophy at the University of St Andrews. In 1876 he was appointed to the Chair of Divinity in Edinburgh which he occupied until he retired in 1903.