Sets question.

You're talking about formal proof system, and I was talking about formula satisfaction in structures.. But equivalent formulas for any structure are equivalent formulas in the formal system. (And conversely, thanks to the completness theorem (Gödel, 1930)).

Has your system 3 original axioms and 2 deduction rules? (plus the predicate calculus tautologies)

The logical thing to do here is close the thread, I think.

Edit:

Quote:

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Originally Posted by archidi

My dear Plato [snip]

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I'm not sure how expensive (dear) Forum Moderator Plato's tutoring rates are so I'm not sure about that observation. I do know we are all fortunate to have his expertise and experience available for free at MHF.

Quote:

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Originally Posted by archidi

[snip]don't you know the answer, or you agree with clic clac's proof??

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Option 3: Maintaining a dignified silence.