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What difference between the truth of a conditional* and its logical validity?

This example is on page 2: "If you arrive at my house before 3pm, then I will give you a ride to the concert." On many* analyses, the sentence could be true without being logically valid. In ...
Curtis Franks's user avatar
1 vote
Accepted

Did Russell had something like the notion of domain in the sense defined now by mathematics textbooks?

We can see Rusell's Theory of Types sketched into Appendix B of Principles (1903) and fully described in Mathematical Logic as Based on the Theory of Types (1908). See III. The Meaning and Range of ...
Mauro ALLEGRANZA's user avatar
3 votes

What difference between the truth of a conditional* and its logical validity?

See Valid formula: "A formula of a formal language is a valid formula if and only if it is true under every possible interpretation of the language. In propositional logic, they are tautologies.&...
Mauro ALLEGRANZA's user avatar
1 vote

Can assumption in Hilbert style proof system be contradictory?

As Conifold points out, you can use contradictory assumptions in natural deduction proofs. You just have to discharge the assumptions in the usual way. But your question asks about a Hilbert style ...
Bumble's user avatar
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