It may seem strange that a deduction can be illogical when — as here the conclusion is entirely sensible. Actually, this is very common. For example, consider: 2+2=22=2 x 2 =4

is nonsense as far as logic goes, but it gives the right answer. All mathematicians know that you can give false proofs of correct statements. What you can’t do — if mathematics is logically consistent, as we fervently hope — is give correct proofs of false statements.

]]>r -> ~q

p -> s

r ->s

Not logical I guess.

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