Test this argument form:

W É X
X É Y
~Y     
W

First display the argument in a linear form:

W É X	X É Y	~Y	W

Then assign T to all the premises and F to the conclusion. Put the truth-values above the premises and conclusion:

T	T	T	F
W É X	X É Y	~Y	W

That is the easy part. Now comes the test. You must figure out the truth values of the simple propositions. This may take some effort. But given the assumption that the premises are true and the conclusion is false, there are some givens: Since the ~Y premise is assumed to be true you can regard Y as true. Also, the W is assumed to be false.

T	T	T	F
W É X	X É Y	~Y	W
f	f	t	f

Can you figure out the truth-value of X? HINT: There is only one possibility for X in the second premise--and the premise be true.

Here is an easy one that you can do on your own:

J É K
~J    
K

This one is not very difficult:

U É (V Ú W)
W É ~U
~U

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Copyright © 1999, Michael Eldridge