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All the ideas for 'What is Logic?st1=Ian Hacking', 'Semantics, Conceptual Role' and 'The Thought: a Logical Enquiry'

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25 ideas

2. Reason / A. Nature of Reason / 5. Objectivity
7740 There exists a realm, beyond objects and ideas, of non-spatio-temporal thoughts [Frege, by Weiner]
2. Reason / D. Definition / 3. Types of Definition
13838 A decent modern definition should always imply a semantics [Hacking]
3. Truth / A. Truth Problems / 2. Defining Truth
19466 The word 'true' seems to be unique and indefinable [Frege]
3. Truth / C. Correspondence Truth / 3. Correspondence Truth critique
19465 There cannot be complete correspondence, because ideas and reality are quite different [Frege]
3. Truth / H. Deflationary Truth / 1. Redundant Truth
19468 The property of truth in 'It is true that I smell violets' adds nothing to 'I smell violets' [Frege]
4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / d. Basic theorems of PL
13833 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking]
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]
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]
7. Existence / A. Nature of Existence / 2. Types of Existence
19470 Thoughts in the 'third realm' cannot be sensed, and do not need an owner to exist [Frege]
7. Existence / D. Theories of Reality / 8. Facts / c. Facts and truths
19471 A fact is a thought that is true [Frege]
9. Objects / A. Existence of Objects / 3. Objects in Thought
9877 Late Frege saw his non-actual objective objects as exclusively thoughts and senses [Frege, by Dummett]
18. Thought / A. Modes of Thought / 1. Thought
19469 We grasp thoughts (thinking), decide they are true (judgement), and manifest the judgement (assertion) [Frege]
8162 Thoughts have their own realm of reality - 'sense' (as opposed to the realm of 'reference') [Frege, by Dummett]
9818 A thought is distinguished from other things by a capacity to be true or false [Frege, by Dummett]
18. Thought / A. Modes of Thought / 9. Indexical Thought
16379 Thoughts about myself are understood one way to me, and another when communicated [Frege]
19. Language / A. Nature of Meaning / 7. Meaning Holism / c. Meaning by Role
18033 The meaning of a representation is its role in thought, perception or decisions [Block]
19. Language / D. Propositions / 2. Abstract Propositions / a. Propositions as sense
19467 A 'thought' is something for which the question of truth can arise; thoughts are senses of sentences [Frege]
19. Language / D. Propositions / 5. Unity of Propositions
19472 A sentence is only a thought if it is complete, and has a time-specification [Frege]