Combining Texts

All the ideas for 'What is Logic?st1=Ian Hacking', 'III.12 On physiognomy' and 'A Dictionary of Philosophy'

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15 ideas

2. Reason / D. Definition / 3. Types of Definition

13838

A decent modern definition should always imply a semantics [Hacking]

4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL

13834

Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking]

13835

Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking]

13833

'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

13845

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

13840

First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking]

13844

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

13842

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

13837

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

13839

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

13843

If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking]

12. Knowledge Sources / B. Perception / 4. Sense Data / a. Sense-data theory

6455	Maybe 'sense-data' just help us to talk about unusual perceptual situations [Lacey]

12. Knowledge Sources / B. Perception / 4. Sense Data / b. Nature of sense-data

6454	Where do sense-data begin or end? Can they change? What sort of thing are they? [Lacey]

6453	Some claim sense-data are public, and are parts of objects [Lacey]

22. Metaethics / B. Value / 2. Values / e. Death

7495	Apart from the fear, dying is an easy duty [Montaigne]