18 ideas
| 10688 | 'Equivocation' is when terms do not mean the same thing in premises and conclusion [Beall/Restall] |
| 9456 | Modal logic is multiple systems, shown in the variety of accessibility relations between worlds [Jacquette] |
| 9457 | The two main views in philosophy of logic are extensionalism and intensionalism [Jacquette] |
| 10690 | Formal logic is invariant under permutations, or devoid of content, or gives the norms for thought [Beall/Restall] |
| 10691 | Logical consequence needs either proofs, or absence of counterexamples [Beall/Restall] |
| 10695 | Logical consequence is either necessary truth preservation, or preservation based on interpretation [Beall/Restall] |
| 10689 | A step is a 'material consequence' if we need contents as well as form [Beall/Restall] |
| 10696 | A 'logical truth' (or 'tautology', or 'theorem') follows from empty premises [Beall/Restall] |
| 9458 | Extensionalists say that quantifiers presuppose the existence of their objects [Jacquette] |
| 9461 | Intensionalists say meaning is determined by the possession of properties [Jacquette] |
| 10693 | Models are mathematical structures which interpret the non-logical primitives [Beall/Restall] |
| 10692 | Hilbert proofs have simple rules and complex axioms, and natural deduction is the opposite [Beall/Restall] |
| 9460 | Extensionalist semantics forbids reference to nonexistent objects [Jacquette] |
| 9459 | Extensionalist semantics is circular, as we must know the extension before assessing 'Fa' [Jacquette] |
| 23169 | Democratic institutions become impossible in a fanatical democracy [Russell] |
| 23170 | Liberal opinions are tentative rather than dogmatic, and are always responsive to new evidence [Russell] |
| 23172 | Empiricist Liberalism is the only view for someone who favours scientific evidence and happiness [Russell] |
| 23171 | Empiricism is ethically superior, because dogmatism favours persecution and hatred [Russell] |