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All the ideas for 'What is Logic?st1=Ian Hacking', 'On the Infinite' and 'Nature and Observability of Causal Relations'

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29 ideas

2. Reason / D. Definition / 2. Aims of Definition
A correct definition is what can be substituted without loss of meaning [Ducasse]
2. Reason / D. Definition / 3. Types of Definition
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
'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]
6. Mathematics / A. Nature of Mathematics / 1. Mathematics
I aim to establish certainty for mathematical methods [Hilbert]
We believe all mathematical problems are solvable [Hilbert]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / a. The Infinite
No one shall drive us out of the paradise the Cantor has created for us [Hilbert]
We extend finite statements with ideal ones, in order to preserve our logic [Hilbert]
Only the finite can bring certainty to the infinite [Hilbert]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / d. Actual infinite
The idea of an infinite totality is an illusion [Hilbert]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / j. Infinite divisibility
There is no continuum in reality to realise the infinitely small [Hilbert]
6. Mathematics / C. Sources of Mathematics / 7. Formalism
The subject matter of mathematics is immediate and clear concrete symbols [Hilbert]
6. Mathematics / C. Sources of Mathematics / 8. Finitism
Mathematics divides in two: meaningful finitary statements, and empty idealised statements [Hilbert]
11. Knowledge Aims / B. Certain Knowledge / 1. Certainty
My theory aims at the certitude of mathematical methods [Hilbert]
26. Natural Theory / C. Causation / 2. Types of cause
Causation is defined in terms of a single sequence, and constant conjunction is no part of it [Ducasse]
26. Natural Theory / C. Causation / 8. Particular Causation / a. Observation of causation
We see what is in common between causes to assign names to them, not to perceive them [Ducasse]
26. Natural Theory / C. Causation / 8. Particular Causation / c. Conditions of causation
Causes are either sufficient, or necessary, or necessitated, or contingent upon [Ducasse]
When a brick and a canary-song hit a window, we ignore the canary if we are interested in the breakage [Ducasse]
26. Natural Theory / C. Causation / 8. Particular Causation / d. Selecting the cause
A cause is a change which occurs close to the effect and just before it [Ducasse]
26. Natural Theory / C. Causation / 9. General Causation / a. Constant conjunction
Recurrence is only relevant to the meaning of law, not to the meaning of cause [Ducasse]
26. Natural Theory / C. Causation / 9. General Causation / b. Nomological causation
We are interested in generalising about causes and effects purely for practical purposes [Ducasse]