The Technique of the Mystery Story

Poe deliberately remarks on Dupin's diseased intelligence, thus providing a defence against any implication that the detective's powers were superhuman.

Analogous to this is Conan Doyle's characterization of Sherlock Holmes.

To quote from "A Study in Scarlet," where Holmes makes his first appearance:

"Well, I have a trade of my own. I suppose I am the only one in the world. I'm a consulting detective, if you can understand what that is. Here in London we have lots of government detectives and lots of private ones. When these fellows are at fault they come to me, and I manage to put them on the right scent. They lay all the evidence before me, and I am generally able, by the help of my knowledge of the history of crime, to set them straight. There is a strong family resemblance about misdeeds, and if you have all the details of a thousand at your finger-ends, it is odd if you can't unravel the thousand and first. Lestrade is a well known detective. He got himself into a fog recently over a forgery case, and that was what brought him here."

"And these other people?"

"They are mostly sent out by private inquiry agencies. They are all people who are in trouble about something, and want a little enlightening I listen to their story, they listen to my comments, and then I pocket my fee."

"But do you mean to say," I said, "that without leaving your room you can unravel some knot which other men can make nothing of, although they have seen every detail for themselves?"

"Quite so. I have a kind of intuition that way. Now and again a case turns up which is a little more complex. Then I have to bustle about and see things with my own eyes. You see, I have a lot of special knowledge which I apply to the problem, and which facilitates matters wonderfully. Those rules of deduction laid down in that article which aroused your scorn are invaluable to me in practical work. Observation with me is second nature."

However, the later detective thus scorns the earlier one when Watson, thinking to flatter, compares Holmes to Dupin:

"No doubt you think that you are complimenting me in comparing me to Dupin," he observed. "Now, in my opinion, Dupin was a very inferior fellow. That trick of his of breaking in on his friends' thoughts with an apropos remark after a quarter of an hour's silence is really very showy and superficial. He had some analytical genius, no doubt; but he was by no means such a phenomenon as Poe appeared to imagine."

"Have you read Gaboriau's works?" I asked. "Does Lecoq come up to your idea of a detective?"

Sherlock Holmes sniffed sardonically.

"Lecoq was a miserable bungler," he said, in an angry voice; "he had only one thing to recommend him, and that was his energy. That book made me positively ill. The question was how to identify an unknown prisoner. I could have done it in twenty-four hours. Lecoq took six months or so. It might be made a text-book for detectives to teach them what to avoid."

But Dupin himself speaks with equal contempt of his predecessor in the profession. He says:

"Vidocq, for example, was a good guesser, and a persevering man. But without educated thought, he erred continually by the very intensity of his investigations. He impaired his vision by holding the object too close. He might see, perhaps, one or two points with unusual clearness, but in so doing he necessarily lost sight of the matter as a whole."

However, as Conan Doyle himself declares:

"In a work which consists in the drawing of detectives," he once wrote, "there are only one or two qualities which one can use, and an author is forced to hark back upon them constantly, so that every detective must really resemble every other detective to a greater or less extent. There is no great originality required in devising or constructing such a man, and the only possible originality which one can get into a story about a detective is in giving him original plots and problems to solve, as in his equipment there must be an alert acuteness of mind to grasp facts and the relation which each of them bears to the other."

The detectives who follow in the straight path trodden by these pioneers are legion.

Among the best known is The Thinking Machine, hero of two series of stories by the late Jacques Futrelle.

The Thinking Machine whose name was Professor Van Dusen was remotely German. For generations his ancestors had been noted in the sciences; he was the logical result of the master mind. First and above all he was a logician. At least thirty-five years of the half-century or so of his existence had been devoted exclusively to proving that two and two always equal four, except in unusual cases, where they equal three or five, as the case may be. He stood broadly on the general proposition that all things that start must go somewhere, and was able to bring the concentrated mental force of his forefathers to bear on a given problem. Incidentally it may be remarked that Professor Van Dusen wore a No. 8 hat.