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Single Idea 13610

[filed under theme 4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / e. Axioms of PL ]

Full Idea

For ¬,→ Schemas: (A1) |-φ→(ψ→φ), (A2) |-(φ→(ψ→ξ)) → ((φ→ψ)→(φ→ξ)), (A3) |-(¬φ→¬ψ) → (ψ→φ), Rule:DET:|-φ,|-φ→ψ then |-ψ

Gist of Idea

A logic with ¬ and → needs three axiom-schemas and one rule as foundation

Source

David Bostock (Intermediate Logic [1997], 5.2)

Book Ref

Bostock,David: 'Intermediate Logic' [OUP 1997], p.194

A Reaction

A1 says everything implies a truth, A2 is conditional proof, and A3 is contraposition. DET is modus ponens. This is Bostock's compact near-minimal axiom system for proposition logic. He adds two axioms and another rule for predicate logic.

Related Idea

Idea 13619 Quantification adds two axiom-schemas and a new rule [Bostock]

The 17 ideas with the same theme [statements treated as true without question]:

2145 In mathematics certain things have to be accepted without further explanation [Plato]
562 Axioms are the underlying principles of everything, and who but the philosopher can assess their truth? [Aristotle]
573 The axioms of mathematics are part of philosophy [Aristotle]
1668 An axiom is a principle which must be understood if one is to learn anything [Aristotle]
20791 Chrysippus has five obvious 'indemonstrables' of reasoning [Chrysippus, by Diog. Laertius]
5620 Philosophy has no axioms, as it is just rational cognition of concepts [Kant]
9154 Frege agreed with Euclid that the axioms of logic and mathematics are known through self-evidence [Frege, by Burge]
9585 Since every definition is an equation, one cannot define equality itself [Frege]
9542 The best known axiomatization of PL is Whitehead/Russell, with four axioms and two rules [Russell/Whitehead, by Hughes/Cresswell]
9013 We can eliminate 'or' from our basic theory, by paraphrasing 'p or q' as 'not(not-p and not-q)' [Quine]
13610 A logic with ¬ and → needs three axiom-schemas and one rule as foundation [Bostock]
8086 Predicate logic retains the axioms of propositional logic [Devlin]
6299 Axioms are often affirmed simply because they produce results which have been accepted [Resnik]
8476 Axiomatization simply picks from among the true sentences a few to play a special role [Orenstein]
7797 Axiom systems of logic contain axioms, inference rules, and definitions of proof and theorems [Girle]
4632 'Natural' systems of deduction are based on normal rational practice, rather than on axioms [Baggini /Fosl]
4631 In ideal circumstances, an axiom should be such that no rational agent could possibly object to its use [Baggini /Fosl]