Abstract

In this paper, (1) I argue that Sherlock Holmes was a good logician according to the standard of his day, and (2) I try to show what his method of reasoning was. Now, (2) is a harder task than (1), because we have to identify the essential features of his method of reasoning. In order to show this, I have not only to examine what Holmes says he is doing, but also to look at the methods of scientific reasoning recommended by several distinguished philosophers of science in the 19th century. I want to examine Holmes's method of reasoning in a historical setting; and this has something to do with the philosophy of science in the 19th century, and hopefully with the philosophy of science today. I will examine whether such methods are similar or dissimilar to Holmes's method. Logicians and philosophers I wish to examine are, John Herschel, John Stuart Mill, William Whewell, Augustus de Morgan, and William Stanley Jevons; however, since the space is limited, I cannot do justice to all of them. My conclusion is this: Sherlock Holmes was distinctly different from Herschel or Mill or Whewell who may be called a classical methodologist; but he was very close to de Morgan or Jevons who were an advocate of the new symbolic logic and the probabilistic theory of induction. But what is the point of showing all this? The rise and development of statistical method in the19th century had a great impact on the theories of scientific reasoning, and de Morgan's or Jevons's theory is a newer theory of induction in this century. And such a change of methodology is clearly reflected in the popular stories of Sherlock Holmes, which were written in the late 19th century and early 20th century.