One of the delightful treasures about Father Brown is the story of how Chesterton got this idea of creating him. Chesterton had been visiting a friend, father John O'Connor, and he was repeatedly stunned by how broad and deep the priest's knowledge of human depravity proved to be. It had been no surprise to him that the Church would know a good deal more than him about good, but that it also knew a good deal more about evil was a shock. After one such meeting, Chesterton overheard a couple of young men saying to one another that they felt it wasn't right for a man to be like that priest and shut himself up all cloistered and cut off from life, that it created a naiveté and ignorance of the world. This was Chesterton's reaction to this irony:
To me, still almost shivering with the appallingly practical facts of which the priest had warned me, this comment came with such a colossal and crushing irony, that I nearly burst into a loud harsh laugh in the drawing-room. For I knew perfectly well that, as regards all the solid Satanism which the priest knew and warred against with all his life, these two Cambridge gentlemen (luckily for them) knew about as much of real evil as two babies in the same perambulator.To this broad experience of the fallen human heart and its consequences, Chesterton added a deep conviction about reason and common sense. He exploded the shallow myth that a churchman must be a bit weak in reason and somewhat gullible simply because he happens to believe in miracles and the supernatural. Chesterton rather proved that point himself in his life: even his atheist friends like George Bernard Shaw considered the Catholic writer to be one of the towering intellects of the 20th century. In his first Father Brown story, The Blue Cross, his priest-detective defends reason against a tall impostor posing as another priest:
As the impostor reveals himself, demanding the priest surrender a holy relic he wants to steal, an exchange takes place where the priest one-ups the thief each time in criminal tricks:
Chesterton wrote some 52 short stories featuring his "dumpy little priest" detective, and for a time in the early 20th Century, Father Brown was nearly as popular as Sherlock Holmes. Part of this charm was due to the very different style and reasoning Chesterton employed in the stories. Father Brown knew what was in his own heart, as a human being corrupted by sin, and therefore he was in a position to deduce the desires, motives, and passions that tempted other men and women to commit crimes. I would be remiss if I didn't give you a link to where Father Brown himself explains his method of solving crimes, but this commentary captures the contrast well:
Father Brown was inspired in part by Chesterton’s good friend Father John O’Connor, a priest in Yorkshire. The central idea was that no other figure was better suited for solving crimes. In one story, the cornered murderer, having listened to Father Brown’s explanation of how he worked out the sinister truth, cries out: ‘How do you know all this? Are you a devil?’
‘I am a man,’ replies Father Brown, ‘and therefore have all devils in my heart.’ ...
The great pleasure of Father Brown is that he represents a step away from the icy inductive logic of Sherlock Holmes. There are still clues, though they do not just stand there as facts; it is how they are interpreted that counts. And the interpretations are frequently paradoxical. On the other side of Father Brown are the sleuths of Agatha Christie — Marple and Poirot — who, while understanding crimes of passion, have nothing in the way of passion themselves. Conversely, Father Brown has an innate, unstoppable optimism; whatever one’s beliefs or non-beliefs, as a narrative device it is very clever.Sinclair McKay, Bring back Father Brown (The Spectator: Dec. 14, 2009).