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Single Idea 10703

[filed under theme 5. Theory of Logic / H. Proof Systems / 3. Proof from Assumptions ]

Full Idea

A 'supposition' axiomatic theory is as concerned with truth as a 'realist' one (with undefined terms), but the truths are conditional. Satisfying the axioms is satisfying the theorem. This is if-thenism, or implicationism, or eliminative structuralism.

Gist of Idea

Supposing axioms (rather than accepting them) give truths, but they are conditional

Source

Michael Potter (Set Theory and Its Philosophy [2004], 01.1)

Book Ref

Potter,Michael: 'Set Theory and Its Philosophy' [OUP 2004], p.8


A Reaction

Aha! I had failed to make the connection between if-thenism and eliminative structuralism (of which I am rather fond). I think I am an if-thenist (not about all truth, but about provable truth).


The 7 ideas with the same theme [proofs which add assumptions to axioms and rules]:

The Deduction Theorem greatly simplifies the search for proof [Bostock]
'Conditonalised' inferences point to the Deduction Theorem: If Γ,φ|-ψ then Γ|-φ→ψ [Bostock]
Proof by Assumptions can always be reduced to Proof by Axioms, using the Deduction Theorem [Bostock]
The Deduction Theorem and Reductio can 'discharge' assumptions - they aren't needed for the new truth [Bostock]
Proof by induction 'on the length of the formula' deconstructs a formula into its accepted atoms [Sider]
Induction has a 'base case', then an 'inductive hypothesis', and then the 'inductive step' [Sider]
Supposing axioms (rather than accepting them) give truths, but they are conditional [Potter]