The trees always blossom in May if April rainfall exceeds 5 centimeters. If April rainfall exceeds 5 centimeters, the...

femon90 July 19, 2018

Flaw

I think the question was written wrong. It doesn't have a flaw.

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Mehran July 19, 2018

@femon90 this argument is definitely flawed!

Let's diagram the stimulus to take a closer look:

P1: The trees always blossom in May if April rainfall exceeds 5 centimeters.

AR > 5cm ==> TBM
not TBM ==> not AR > 5cm

P2: If April rainfall exceeds 5 centimeters, then the reservoirs are always full on May 1.

AR > 5cm ==> RF May 1st
not RF May 1st ==> not AR > 5cm

C: The reservoirs were not full this May 1 and thus the trees will not blossom this May.

not RF May 1st ==> not TBM

The flaw here is the incorrect reversal taking place in P1 after invoking the contrapositive of P2.

If the reservoirs are not full this May 1, we know that April rainfall did not exceed 5 centimeters.

But April rainfall not exceeding 5 centimeters is our necessary condition in P1 so it tells us nothing else.

Remember, DON'T JUST REVERSE!

Hope that helps! Please let us know if you have any other questions.