But when they are not ex-policemen, they are always ex-something else, since there is no college for detectives, and it is not probable that any young man ever deliberately began life with the intention of becoming one.

Edgar Poe invented the amateur detective, and modern writers have developed him till he is a familiar and always striking figure in fiction and on the stage.

Whether he really exists or not does not matter.

I have heard a great living painter ask the question: What has art to do with truth?
But as a matter of fact Paul Griggs, who had seen a vast deal, had never met an amateur detective; and my own impression is that if one existed he would instantly turn himself into a professional because it would be so very profitable.
The one who called on Griggs in his lodgings wrote 'barrister-at-law' after his name, and had the right to do so.

He had languished in chambers, briefless and half starving, either because he had no talent for the bar, or because he had failed to marry a solicitor's daughter.
He himself was inclined to attribute his want of success to the latter cause.