What's In Your Fridge?

Sherlock Holmes was a master of inference. Here's Holmes at work in A Study in Scarlet:

I knew you came from Afghanistan. From long habit the train of thoughts ran so swiftly through my mind that I arrived at the conclusion without being conscious of intermediate steps. There were such steps, however. The train of reasoning ran, "Here is a gentle­ man of a medical type, but with the air of a military man. Clearly an army doctor, then. He has just come from the tropics, for his face is dark, and that is not the natural tint of his skin, for his wrists are fair. He has undergone hardship and sickness, as his haggard face says clearly. His left arm has been injured. He holds it in a stiff and unnatural manner.. Where in the tropics would an English army doctor have seen much hardship and got his arm wounded? Clearly in Afghanistan." The whole train of thought did not occupy a second. I then remarked that you came from Afghanistan, and you were astonished.

Although this passage appears in a chapter entitled "The Science of Deduction," Holmes is not using deduction here because the truth of the premises does not guarantee the truth of the conclusion. From the fact that Watson has a deep tan and a wounded arm, it doesn't necessarily follow that he has been in Afghanistan. He could have been in California and cut himself surfing. Properly speaking, Holmes is using abduction, or inference to the best explanation, because he arrives at his conclusion by citing a number of facts and coming up with the hypothesis that best explains them.