I propose to devote my declining years to the composition of a textbook which shal focus the whole art of detection into one volume.
—Sherlock Holmes in The Adventure of the Abbey Grange
He is a Logician
A logician studies the way we ought to reason; she is interested in the distinction between corect reasoning and incorect reasoning. Although we al reason and are often interested in whether our reasoning is valid we are not a l logicians because we do not make a study of it; that is, we do not reflect deeply enough on this subject.
Now Sherlock Holmes reasons a great deal—Watson cals him the greatest reasoning machine in the world. But he not only reasons he also reflects on…show more content… In one of the articles he has published Sherlock Holmes has this to say concerning the power of this kind of reasoning From a drop of water … . a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other. A Study in Scarlet
Things scientists know are not confined to things they have seen or heard. Scientists are able to tel us what happened milions of years ago—just as Sherlock Holmes is able to tel us what happened when a crime was commited. Now how is this done if not by reasoning? There are two ways for us to know: either directly or by inference. Since scientists were not there milions of years ago; since Sherlock Holmes was not there when the crime was commited; they could not have known what they know directly. They have to rely on reasoning. It is through reasoning that they find out what they want to know.
Sherlock Holmes is aware that he engages in a special form of reasoning—special when compared to the kind we ordinarily do. He cals it reasoning backwards.
In solving a problem of this sort, the grand thing is to be able to reason backwards. That is a very useful accomplishment, and a very easy one, but people do not practise it much. In the everyday affairs of life it is more useful to reason forward, and so the other comes to be neglected. There are fifty who can reason syntheticaly for one who can reason analyticaly.