How would I deduce a≠c from the premises a≠b and b≠c in Fitch? This is what I've done so far.

b=b (=Intro)

b≠a (Ana Con)

b≠c (Reit)

And then for some reason I get stuck here? I know this sounds simple, but I'm lost! Thanks in advance.

1 Answer 1


You can't, because it isn't valid. Think about it with numbers, consider:


It's true that a≠b & b≠c, yet a=c.

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