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All the ideas for 'What is Logic?st1=Ian Hacking', 'Letters to Varignon' and 'Ordinary Objects'

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33 ideas

2. Reason / D. Definition / 3. Types of Definition
A decent modern definition should always imply a semantics [Hacking]
3. Truth / B. Truthmakers / 12. Rejecting Truthmakers
Maybe analytic truths do not require truth-makers, as they place no demands on the world [Thomasson]
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 / B. Logical Consequence / 6. Entailment
Analytical entailments arise from combinations of meanings and inference rules [Thomasson]
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 / A. Nature of Existence / 6. Criterion for Existence
Existence might require playing a role in explanation, or in a causal story, or being composed in some way [Thomasson]
7. Existence / D. Theories of Reality / 11. Ontological Commitment / a. Ontological commitment
Rival ontological claims can both be true, if there are analytic relationships between them [Thomasson]
7. Existence / D. Theories of Reality / 11. Ontological Commitment / d. Commitment of theories
Theories do not avoid commitment to entities by avoiding certain terms or concepts [Thomasson]
9. Objects / A. Existence of Objects / 1. Physical Objects
Ordinary objects may be not indispensable, but they are nearly unavoidable [Thomasson]
The simple existence conditions for objects are established by our practices, and are met [Thomasson]
9. Objects / A. Existence of Objects / 6. Nihilism about Objects
It is analytic that if simples are arranged chair-wise, then there is a chair [Thomasson, by Hofweber]
Ordinary objects are rejected, to avoid contradictions, or for greater economy in thought [Thomasson]
To individuate people we need conventions, but conventions are made up by people [Thomasson]
Eliminativists haven't found existence conditions for chairs, beyond those of the word 'chair' [Thomasson]
9. Objects / B. Unity of Objects / 1. Unifying an Object / c. Unity as conceptual
Wherever an object exists, there are intrinsic properties instantiating every modal profile [Thomasson]
9. Objects / B. Unity of Objects / 3. Unity Problems / c. Statue and clay
If the statue and the lump are two objects, they require separate properties, so we could add their masses [Thomasson]
Given the similarity of statue and lump, what could possibly ground their modal properties? [Thomasson]
9. Objects / F. Identity among Objects / 6. Identity between Objects
Identity claims between objects are only well-formed if the categories are specified [Thomasson]
Identical entities must be of the same category, and meet the criteria for the category [Thomasson]
10. Modality / C. Sources of Modality / 3. Necessity by Convention
Modal Conventionalism says modality is analytic, not intrinsic to the world, and linguistic [Thomasson]
12. Knowledge Sources / E. Direct Knowledge / 1. Common Sense
A chief task of philosophy is making reflective sense of our common sense worldview [Thomasson]
19. Language / B. Reference / 3. Direct Reference / b. Causal reference
How can causal theories of reference handle nonexistence claims? [Thomasson]
Pure causal theories of reference have the 'qua problem', of what sort of things is being referred to [Thomasson]
19. Language / E. Analyticity / 1. Analytic Propositions
Analyticity is revealed through redundancy, as in 'He bought a house and a building' [Thomasson]
27. Natural Reality / G. Biology / 3. Evolution
Men are related to animals, which are related to plants, then to fossils, and then to the apparently inert [Leibniz]