2.9: Collaborative Activity

When one thinks of deduction, one often thinks of the fictional character Sherlock Holmes, a detective introduced by British author Sir Arthur Conan Doyle in the 1887 novel A Study in Scarlet. One of the reasons why Sherlock Holmes became so famous and so memorable is that the character was inspired by Joseph Bell, a surgeon at the Royal Infirmary of Edinburgh. Conan Doyle met Dr. Bell in 1877 and worked for him as a clerk. Dr. Bell was noted for drawing broad conclusions from minute observations. The character of Holmes is also known for making such conclusions, often to the surprise of those around him. In reading the stories, one finds that Holmes uses both deduction and induction in making his conclusions.

In this collaborative activity, you and your group will read a passage from the short story “The Red Headed League,” which was written by Conan Doyle and published in the Strand Magazine in August 1891. In the story, Holmes’ associate Dr. Watson arrives at their quarters to find Holmes talking to Jabez Wilson, a London pawnbroker. Holmes invites Watson to stay for the consultation at which point we pick up the story.

I did not gain very much, however, by my inspection. Our visitor bore every mark of being an average commonplace British tradesman, obese, pompous, and slow. He wore rather baggy gray shepherd's check trousers, a not over-clean black frock coat, unbuttoned in the front, and a drab waistcoat with a heavy brassy Albert chain, and a square pierced bit of metal dangling down as an ornament. A frayed top hat and a faded brown overcoat with a wrinkled velvet collar lay upon a chair beside him. Altogether, look as I would, there was nothing remarkable about the man save his blazing red head and the expression of extreme chagrin and discontent upon his features.

Sherlock Holmes's quick eye took in my occupation, and he shook his head with a smile as he noticed my questioning glances. "Beyond the obvious facts that he has at some time done manual labor, that he takes snuff, that he is a Freemason, that he has been in China, and that he has done a considerable amount of writing lately, I can deduce nothing else."

Mr. Jabez Wilson started up in his chair, with his forefinger upon the paper, but his eyes upon my companion.

How, in the name of good fortune, did you know all that, Mr. Holmes?" he asked. "How did you know, for example, that I did manual labor? It's as true as gospel, for I began as a ship's carpenter."

"Your hands, my dear sir. Your right hand is quite a size larger than your left. You have worked with it and the muscles are more developed."

"Well, the snuff, then, and the Freemasonry?"

"I won't insult your intelligence by telling you how I read that, especially as, rather against the strict rules of your order, you use an arc and compass breastpin."

"Ah, of course, I forgot that. But the writing?"

"What else can be indicated by that right cuff so very shiny for five inches, and the left one with the smooth patch near the elbow where you rest it upon the desk."

"Well, but China?"

"The fish which you have tattooed immediately above your wrist could only have been done in China. I have made a small study of tattoo marks, and have even contributed to the literature of the subject. That trick of staining the fishes' scales of a delicate pink is quite peculiar to China. When, in addition, I see a Chinese coin hanging from your watch chain, the matter becomes even more simple."

Mr. Jabez Wilson laughed heavily. "Well, I never!" said he. "I thought at first that you had done something clever, but I see that there was nothing in it after all."

For this activity have one member of your group read the passage out loud to the other group members. After reading the passage the group should identify each spot where Holmes draws a conclusion from what was observed about the appearance of Mr. Wilson. Discuss each conclusion, answering the following questions for each:

1. Is the conclusion based on inductive or deductive reasoning?
2. Are there other possible explanations for each conclusion? In other words, is it possible that Holmes could be wrong?
3. How does the role of reasoning to the best explanation play a part in the conclusions that Holmes makes?