Thursday, March 30, 2017

How to analyze this sentence’s logic: “If it rains, I'll take an umbrella.”



A person was asked to analyze the following sentence, but couldn't answer even after some searching. They did not understand that this was a logic puzzle.



If it rains, I'll take an umbrella.



How would one analyze the truth table of the logic of this sentence?



Answer



This is a classic example used in logic. See Google Search: "if p then q" rains umbrella



If it rains, (then) I'll take an umbrella.




If p then q.
p = it rains
q = I'll take an umbrella.


Statement is true or false accordingly:



  • True: It rains and I take my umbrella.

  • False: It rains and I don't take my umbrella.

  • True: It doesn't rain and I take my umbrella.

  • True: It doesn't rain and I don't take my umbrella.



Note the abbreviated rule:



  • True: It doesn't rain. (It doesn't matter if I take my umbrella.)


Note the equivalent statement: "I take my umbrella OR it doesn't rain." (Non-exclusive "or")




Also note the alternative logic of Murphey's Law: A corollary of Murphy's Law says, "If I don't take my umbrella, it'll rain." (Credit to @J.R.)


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