Combining Texts

All the ideas for 'What is Logic?st1=Ian Hacking', 'Tarski on Truth and Logical Consequence' and 'The Extended Mind'

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18 ideas

2. Reason / D. Definition / 3. Types of Definition
A decent modern definition should always imply a semantics [Hacking]
3. Truth / F. Semantic Truth / 1. Tarski's Truth / c. Meta-language for truth
'Snow is white' depends on meaning; whether snow is white depends on snow [Etchemendy]
3. Truth / G. Axiomatic Truth / 1. Axiomatic Truth
We can get a substantive account of Tarski's truth by adding primitive 'true' to the object language [Etchemendy]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking]
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]
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]
11. Knowledge Aims / A. Knowledge / 4. Belief / a. Beliefs
A notebook counts as memory, if is available to consciousness and guides our actions [Clark/Chalmers]
15. Nature of Minds / A. Nature of Mind / 6. Anti-Individualism
A mechanism can count as 'cognitive' whether it is in the brain or outside it [Clark/Chalmers, by Rowlands]
If something in the world could equally have been a mental process, it is part of our cognition [Clark/Chalmers]
Consciousness may not extend beyond the head, but cognition need not be conscious [Clark/Chalmers]
16. Persons / D. Continuity of the Self / 2. Mental Continuity / a. Memory is Self
If a person relies on their notes, those notes are parted of the extended system which is the person [Clark/Chalmers]