Combining Texts

All the ideas for 'What is Logic?st1=Ian Hacking', 'Letter to Mersenne' and 'Outline of a Theory of Truth'

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17 ideas

2. Reason / D. Definition / 3. Types of Definition
A decent modern definition should always imply a semantics [Hacking]
3. Truth / F. Semantic Truth / 2. Semantic Truth
Kripke's semantic theory has actually inspired promising axiomatic theories [Kripke, by Horsten]
Kripke offers a semantic theory of truth (involving models) [Kripke, by Horsten]
3. Truth / G. Axiomatic Truth / 1. Axiomatic Truth
Certain three-valued languages can contain their own truth predicates [Kripke, by Gupta]
The Tarskian move to a metalanguage may not be essential for truth theories [Kripke, by Gupta]
3. Truth / G. Axiomatic Truth / 3. KF Truth Axioms
Kripke classified fixed points, and illuminated their use for clarifications [Kripke, by Halbach]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking]
Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking]
'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking]
5. Theory of Logic / A. Overview of Logic / 4. Pure Logic
The various logics are abstractions made from terms like 'if...then' in English [Hacking]
5. Theory of Logic / A. Overview of Logic / 5. First-Order Logic
First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking]
A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking]
5. Theory of Logic / A. Overview of Logic / 7. Second-Order Logic
Second-order completeness seems to need intensional entities and possible worlds [Hacking]
5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / a. Logical connectives
With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking]
5. Theory of Logic / E. Structures of Logic / 4. Variables in Logic
Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking]
5. Theory of Logic / J. Model Theory in Logic / 3. Löwenheim-Skolem Theorems
If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking]
16. Persons / F. Free Will / 3. Constraints on the will
The more reasons that compel me, the freer I am [Descartes]