Combining Texts

All the ideas for 'What is Logic?st1=Ian Hacking', 'Introduction - Ontology' and 'On the Essence of Truth'

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


17 ideas

2. Reason / D. Definition / 3. Types of Definition
A decent modern definition should always imply a semantics [Hacking]
3. Truth / A. Truth Problems / 1. Truth
For Heidegger there is 'ontic' truth or 'uncoveredness', as in "he is a true friend" [Heidegger, by Wrathall]
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]
7. Existence / C. Structure of Existence / 3. Levels of Reality
Biologists see many organic levels, 'abstract' if seen from below, 'structural' if seen from above [Lycan]
9. Objects / F. Identity among Objects / 6. Identity between Objects
'Lightning is electric discharge' and 'Phosphorus is Venus' are synthetic a posteriori identities [Lycan]
17. Mind and Body / C. Functionalism / 2. Machine Functionalism
Functionalism has three linked levels: physical, functional, and mental [Lycan]
17. Mind and Body / C. Functionalism / 5. Teleological Functionalism
A mental state is a functional realisation of a brain state when it serves the purpose of the organism [Lycan]
26. Natural Theory / A. Speculations on Nature / 2. Natural Purpose / c. Purpose denied
People are trying to explain biological teleology in naturalistic causal terms [Lycan]