The recent Mutant City Blues reboot offers the option of playing as a heightened private detective in this brave new world of superpowers and those who abuse them, and that got me thinking: just what is a private detective, anyway?
The oldest examples are crooks who went straight - sort of. Men like France's Eugène François Vidocq, a rakehell, soldier, convict, probable forger, duelist and martial artist who turned his life around and, in 1811, joined the cops. Later, when the Sûreté decided in 1833 that it didn't need recruits with a criminal history, Vidocq formed his own investigative agency, Le bureau des renseignements, made up mainly of ex-cons like himself. Larger than life and full of devilment, Vidocq became the subject of plays, books, gossip, and several films, from the silent era to modern day.
His English equivalent is Jonathon Wild, Thief-Taker General, who operated roughly a century before Vidocq but without the latter's successful career. Less a crook gone straight, more a crook gone even more crooked, this gang boss decided that, in the absence of a police force, he'd act as the police. This allowed Wild endless opportunities for bribe-taking, racketeering and bounty hunting. Wild would offer to find and return stolen goods, and then extract cash from the thieves and the putative owners, threatening to expose criminals or actually turning them over for the bounty on their heads. It all came crashing down when Londoners started taking corruption seriously, for the first and possibly last time, and Wild went to the gallows in 1725, later ending up on the dissection table. His skeleton is possibly the most famous one in the collection of the Royal College of Surgeons.
In the United States the most famous private investigator is Allen Pinkerton, a cooper (maker of barrels) who by chance discovered a gang of counterfeiters, informed on them, and as a result became a Chicago police detective. From there he went from strength to strength, eventually becoming Lincoln's spymaster in the Civil War, a union buster and a terror to train robbers and bandits. The agency he founded still exists today, and became synonymous with private investigation - the Pinkertons.
The earliest fictional detectives tend to operate along these lines, albeit slightly more respectably. Poe's Auguste Dupin is a man born to money but now poor, a kind of gentleman detective who can operate in both the respectable and less-respectable realms because he belongs to both, by training and circumstance. He shares this quality with Sherlock Holmes, whose antecedents might be of the squirearchy but whose financial constraints lead him to make money the best way he can.
Holmes' creator Conan Doyle was himself comfortably middle class, but spent his early life in straitened circumstances due to his father's alcoholism and spent much of his early career bouncing from failed job to failed job before finding a niche in fiction. Whereas Dashiell Hammett left school at age 13 to work, eventually becoming a Pinkerton himself and, later, a soldier, before ever committing a fiction, and Hammett's protagonists are fiercely independent fixers and private agents. His contemporary Raymond Chandler had a decidedly rosier early life, but again financial woes intervened and he turned to writing to solve his cash problems, creating fictional characters like Philip Marlowe, world-weary intermediaries between the rich and those who would prey on the rich.