Combining Texts

All the ideas for 'What is Logic?st1=Ian Hacking', 'fragments/reports' and 'Aristotle on Essence and Explanation'

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

17 ideas

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]
9. Objects / D. Essence of Objects / 7. Essence and Necessity / b. Essence not necessities
11993 Jones may cease to exist without some simple property, but that doesn't make it essential [Kung]
9. Objects / D. Essence of Objects / 7. Essence and Necessity / c. Essentials are necessary
11997 A property may belong essentially to one thing and contingently to another [Kung]
9. Objects / D. Essence of Objects / 8. Essence as Explanatory
11992 Aristotelian essences underlie a thing's existence, explain it, and must belong to it [Kung]
14. Science / D. Explanation / 2. Types of Explanation / k. Explanations by essence
11995 Some peripheral properties are explained by essential ones, but don't themselves explain properties [Kung]
11996 Some non-essential properties may explain more than essential-but-peripheral ones do [Kung]
23. Ethics / A. Egoism / 1. Ethical Egoism
3031 The greatest good is not the achievement of desire, but to desire what is proper [Menedemus, by Diog. Laertius]