Combining Texts

All the ideas for 'Logical Consequence', 'Relations' and 'The Laws of Thought'

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19 ideas

4. Formal Logic / A. Syllogistic Logic / 2. Syllogistic Logic
10688 'Equivocation' is when terms do not mean the same thing in premises and conclusion [Beall/Restall]
4. Formal Logic / B. Propositional Logic PL / 1. Propositional Logic
8083 Boole applied normal algebra to logic, aiming at an algebra of thought [Boole, by Devlin]
7727 Boole's notation can represent syllogisms and propositional arguments, but not both at once [Boole, by Weiner]
5. Theory of Logic / A. Overview of Logic / 2. History of Logic
8686 Boole made logic more mathematical, with algebra, quantifiers and probability [Boole, by Friend]
5. Theory of Logic / A. Overview of Logic / 4. Pure Logic
10690 Formal logic is invariant under permutations, or devoid of content, or gives the norms for thought [Beall/Restall]
5. Theory of Logic / B. Logical Consequence / 2. Types of Consequence
10691 Logical consequence needs either proofs, or absence of counterexamples [Beall/Restall]
5. Theory of Logic / B. Logical Consequence / 4. Semantic Consequence |=
10695 Logical consequence is either necessary truth preservation, or preservation based on interpretation [Beall/Restall]
5. Theory of Logic / B. Logical Consequence / 8. Material Implication
10689 A step is a 'material consequence' if we need contents as well as form [Beall/Restall]
5. Theory of Logic / H. Proof Systems / 2. Axiomatic Proof
22277 Boole's method was axiomatic, achieving economy, plus multiple interpretations [Boole, by Potter]
5. Theory of Logic / I. Semantics of Logic / 3. Logical Truth
10696 A 'logical truth' (or 'tautology', or 'theorem') follows from empty premises [Beall/Restall]
5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models
10693 Models are mathematical structures which interpret the non-logical primitives [Beall/Restall]
6. Mathematics / B. Foundations for Mathematics / 2. Proof in Mathematics
10692 Hilbert proofs have simple rules and complex axioms, and natural deduction is the opposite [Beall/Restall]
8. Modes of Existence / A. Relations / 1. Nature of Relations
21339 We want the ontology of relations, not just a formal way of specifying them [Heil]
21349 Two people are indirectly related by height; the direct relation is internal, between properties [Heil]
21340 Maybe all the other features of the world can be reduced to relations [Heil]
8. Modes of Existence / A. Relations / 2. Internal Relations
21348 In the case of 5 and 6, their relational truthmaker is just the numbers [Heil]
21351 Truthmaking is a clear example of an internal relation [Heil]
21344 If R internally relates a and b, and you have a and b, you thereby have R [Heil]
8. Modes of Existence / C. Powers and Dispositions / 4. Powers as Essence
21350 If properties are powers, then causal relations are internal relations [Heil]