Combining Texts

All the ideas for 'What is Logic?st1=Ian Hacking', 'The Common-Sense View of Reality' and 'Sentences'

expand these ideas     |    start again     |     specify just one area for these texts

20 ideas

1. Philosophy / E. Nature of Metaphysics / 2. Possibility of Metaphysics
20728 Metaphysics is hopeless with its present epistemology; common-sense realism is needed [Colvin]
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
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 / D. Theories of Reality / 2. Realism
20726 We can only distinguish self from non-self if there is an inflexible external reality [Colvin]
20727 Common-sense realism rests on our interests and practical life [Colvin]
7. Existence / D. Theories of Reality / 4. Anti-realism
20729 Arguments that objects are unknowable or non-existent assume the knower's existence [Colvin]
20730 If objects are doubted because their appearances change, that presupposes one object [Colvin]
20731 The idea that everything is relations is contradictory; relations are part of the concept of things [Colvin]
8. Modes of Existence / A. Relations / 1. Nature of Relations
18528 The single imagined 'interval' between things only exists in the intellect [Auriol]
26. Natural Theory / A. Speculations on Nature / 6. Early Matter Theories / b. Prime matter
16589 Prime matter lacks essence, but is only potentially and indeterminately a physical thing [Auriol]
28. God / A. Divine Nature / 4. Divine Contradictions
16651 God can do anything non-contradictory, as making straightness with no line, or lightness with no parts [Auriol]