Yes, the lyrics to this delightful song by Santana (featuring the always forgettable Rob Thomas) share a truly fascinating phenomenon. It is the belief or need for reason merely because of the existance of one’s true love…or, in my case, a Cryptanalysis course.

While studying common methods for cryptography, there was quite a debate when discussing how humans crack the Caeser Cipher. Everyone seemed to have a strong opinion on whether the method was induction or deduction that humans would use to experiment with various 2- and 3-letter word possibilities, as you do in my mother’s personal vice: the cryptogram.

As I pointed out, to much derisive laughter, it’s neither. The correct form of reasoning to use here is abduction. This kind of methodology is not as pure as its bother and sister, deduction and induction, as it can lead to incorrect results. However, this sort of reasoning is arguably the most visible in our modern society. In particular, mysteries and detective-work almost always begin with a great deal of abductive reasoning. A trick to remembering these is to walk through a scenario. Here’s one that I made up:

Sherlock Holmes went to his friends house for tea and found his friend laying in the entrance with a gash on his head and a bloody candlestick next to him; he was dead. Using abductive logic, he could guess that he was struck and killed by the candlestick. It is possible that he died some other way, and that may not even be his blood on the candlestick, but it is fairly reasonable to make that step. Based on this, he could could also use inductive reasoning to estimate that a human struck him (a fairly strong induction as Sherlock remembers only 1 in 200 beating victims that he’s seen attacked by an animal).

Sherlock then remembers that his friend’s will stated that ‘if I die, my butler will take over and own my estate’. Since the man is dead, the butler must own the estate. This fine bit of deductive reasoning tells Sherlock It’s probably a good idea for him to go talk to the butler.