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All the ideas for 'What is Logic?st1=Ian Hacking', 'Criterion of Validity in Reasoning' and 'Identity, Ostension, and Hypostasis'

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27 ideas

1. Philosophy / E. Nature of Metaphysics / 6. Metaphysics as Conceptual
We aren't stuck with our native conceptual scheme; we can gradually change it [Quine]
2. Reason / A. Nature of Reason / 4. Aims of Reason
I reason in order to avoid disappointment and surprise [Peirce]
2. Reason / D. Definition / 3. Types of Definition
A decent modern definition should always imply a semantics [Hacking]
3. Truth / H. Deflationary Truth / 1. Redundant Truth
That a judgement is true and that we judge it true are quite different things [Peirce]
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 / 3. Value of Logic
Only study logic if you think your own reasoning is deficient [Peirce]
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]
7. Existence / B. Change in Existence / 2. Processes
A river is a process, with stages; if we consider it as one thing, we are considering a process [Quine]
7. Existence / C. Structure of Existence / 7. Abstract/Concrete / a. Abstract/concrete
We don't say 'red' is abstract, unlike a river, just because it has discontinuous shape [Quine]
7. Existence / D. Theories of Reality / 8. Facts / a. Facts
Facts are hard unmoved things, unaffected by what people may think of them [Peirce]
7. Existence / D. Theories of Reality / 11. Ontological Commitment / a. Ontological commitment
General terms don't commit us ontologically, but singular terms with substitution do [Quine]
7. Existence / E. Categories / 5. Category Anti-Realism
Discourse generally departmentalizes itself to some degree [Quine]
8. Modes of Existence / E. Nominalism / 4. Concept Nominalism
Understanding 'is square' is knowing when to apply it, not knowing some object [Quine]
8. Modes of Existence / E. Nominalism / 6. Mereological Nominalism
'Red' is a single concrete object in space-time; 'red' and 'drop' are parts of a red drop [Quine]
Red is the largest red thing in the universe [Quine]
9. Objects / F. Identity among Objects / 1. Concept of Identity
To unite a sequence of ostensions to make one object, a prior concept of identity is needed [Quine]
9. Objects / F. Identity among Objects / 7. Indiscernible Objects
We should just identify any items which are indiscernible within a given discourse [Quine]
18. Thought / D. Concepts / 5. Concepts and Language / b. Concepts are linguistic
Concepts are language [Quine]
18. Thought / E. Abstraction / 1. Abstract Thought
Apply '-ness' or 'class of' to abstract general terms, to get second-level abstract singular terms [Quine]