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2. Sherlock Holmes as a logician
We can find many words in Holmes stories which may be used as an evidence for showing that he was a logician. First of all, he frequently characterizes himself as a logician. Quotation Q0 is one of such examples. Here, he speaks of what a logician can do, as well as of what a logician should do. It is certainly a typical task of a logician to do "deduction and analysis," and he or she should work hard in order to be a good logician!
And secondly, many of his words clearly show his stance as a logician. The following quotations are typical examples:
(Q1) "Some facts should be suppressed, or at least, a just sense of proportion should be observed in treating them. The only point in the case which deserved mention was the curious analytical reasoning from effects to causes, by which I succeeded in unravelling it." [The Sign of Four, ch.1]
(Q2) "it is not really difficult to construct a series of inferences, each dependent upon its predecessor and each simple in itself. If, after doing so, one simply knocks out all the central inferences and presents one's audience with the starting-point and the conclusion, one may produce a startling, though possibly a meretricious, effect. " [The Adventure of the Dancing Men]
Quotation Q1 shows where his interest is, when he reads a report of criminal investigations; and since he is only interested in the method of reasoning, it is clear that his stance is nothing but a logician's.
Quotation Q2 shows, again, his stance as a logician, because he analyzes a certain effect of logical reasoning; and his analysis and observation touch upon some of the essential characteristics of logical reasoning. Each single step of logical reasoning is so easy, so obvious; but by combining such easy steps two or three, you lose sight of the necessary connection between the premisses and the conclusion. Take an extreme example: before 1931, who could see such a result as Goedel's Theorem may be obtained?
Thus, my hypothesis that Holmes was a good logician seems very promising. But its proof may not be sufficient; so let us continue our examination, getting into more specific features of his reasoning and his opinions about what he is doing.
June 21, 1998; last modified, April 16, 2006. (c) Soshichi Uchii
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