Elementary

In continuing with my explanation of logical reasoning as they can apply to detective work I'll be reviewing the differences in deduction, abduction, and induction.

Last post I stated that Sherlock incorrectly refers to his brand of logical reasoning as deduction, when it is, in fact, abductive reasoning. What's the difference? Well, deduction (in boring formula form) is deriving b from a, where b is a formal consequence of a. For example, if only female lions can get pregnant and a lion is pregnant, then that lion must be female. Given the truth of the assumption, the deduction is consequently true. Abduction is slightly different in that the truth of the  assumption is not guaranteed, and  therefore our abduction is also not guaranteed. For example, if you happen to see someone laying at the bottom of a flight of stairs, you could assume they tripped and fell, when  in fact they could have been pushed, or perhaps they simply enjoy napping at the bottom of the stairs. The person falling down the stairs is the hypothesis that explains our observation, but only one of many. Induction is also different in that our observations may give us good cause to believe something, though our conclusion may not be true. For example, a person might assume all fish swim underwater because all the fish they've seen thus far swim underwater. This same person would then be quite startled to see fish walking on land and gliding over the ocean.

That concludes my explanation of the three forms of logical reasoning. Next post I'll dive into a different, as yet to be determined, topic.