Combining Philosophers

Ideas for Jean-Jacques Rousseau, Bob Hale and Anon (Gilg)

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5. Theory of Logic / H. Proof Systems / 4. Natural Deduction
Unlike axiom proofs, natural deduction proofs needn't focus on logical truths and theorems [Hale]
     Full Idea: In contrast with axiomatic systems, in natural deductions systems of logic neither the premises nor the conclusions of steps in a derivation need themselves be logical truths or theorems of logic.
     From: Bob Hale (Necessary Beings [2013], 09.2 n7)
     A reaction: Not sure I get that. It can't be that everything in an axiomatic proof has to be a logical truth. How would you prove anything about the world that way? I'm obviously missing something.