53 ideas
| 11051 | Frege's logical approach dominates the analytical tradition [Hanna] |
| 11054 | Scientism says most knowledge comes from the exact sciences [Hanna] |
| 1812 | All discussion is full of uncertainty and contradiction (Mode 11) [Agrippa, by Diog. Laertius] |
| 1811 | Proofs often presuppose the thing to be proved (Mode 15) [Agrippa, by Diog. Laertius] |
| 1813 | All reasoning endlessly leads to further reasoning (Mode 12) [Agrippa, by Diog. Laertius] |
| 1815 | Reasoning needs arbitrary faith in preliminary hypotheses (Mode 14) [Agrippa, by Diog. Laertius] |
| 11071 | 'Affirming the consequent' fallacy: φ→ψ, ψ, so φ [Hanna] |
| 11070 | 'Denying the antecedent' fallacy: φ→ψ, ¬φ, so ¬ψ [Hanna] |
| 11088 | We can list at least fourteen informal fallacies [Hanna] |
| 11059 | Circular arguments are formally valid, though informally inadmissible [Hanna] |
| 11089 | Formally, composition and division fallacies occur in mereology [Hanna] |
| 13520 | A 'tautology' must include connectives [Wolf,RS] |
| 13524 | Deduction Theorem: T∪{P}|-Q, then T|-(P→Q), which justifies Conditional Proof [Wolf,RS] |
| 13521 | Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance [Wolf,RS] |
| 13522 | Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [Wolf,RS] |
| 13523 | Existential Generalization (or 'proof by example'): if we can say P(t), then we can say something is P [Wolf,RS] |
| 13529 | Empty Set: ∃x∀y ¬(y∈x). The unique empty set exists [Wolf,RS] |
| 13526 | Comprehension Axiom: if a collection is clearly specified, it is a set [Wolf,RS] |
| 11058 | Logic is explanatorily and ontologically dependent on rational animals [Hanna] |
| 11072 | Logic is personal and variable, but it has a universal core [Hanna] |
| 13534 | In first-order logic syntactic and semantic consequence (|- and |=) nicely coincide [Wolf,RS] |
| 13535 | First-order logic is weakly complete (valid sentences are provable); we can't prove every sentence or its negation [Wolf,RS] |
| 11061 | Intensional consequence is based on the content of the concepts [Hanna] |
| 13519 | Model theory uses sets to show that mathematical deduction fits mathematical truth [Wolf,RS] |
| 13531 | Model theory reveals the structures of mathematics [Wolf,RS] |
| 13532 | Model theory 'structures' have a 'universe', some 'relations', some 'functions', and some 'constants' [Wolf,RS] |
| 13533 | First-order model theory rests on completeness, compactness, and the Löwenheim-Skolem-Tarski theorem [Wolf,RS] |
| 13537 | An 'isomorphism' is a bijection that preserves all structural components [Wolf,RS] |
| 13539 | The LST Theorem is a serious limitation of first-order logic [Wolf,RS] |
| 13538 | If a theory is complete, only a more powerful language can strengthen it [Wolf,RS] |
| 13525 | Most deductive logic (unlike ordinary reasoning) is 'monotonic' - we don't retract after new givens [Wolf,RS] |
| 13530 | An ordinal is an equivalence class of well-orderings, or a transitive set whose members are transitive [Wolf,RS] |
| 13518 | Modern mathematics has unified all of its objects within set theory [Wolf,RS] |
| 11063 | Logicism struggles because there is no decent theory of analyticity [Hanna] |
| 11055 | Supervenience can add covariation, upward dependence, and nomological connection [Hanna] |
| 11083 | A sentence is necessary if it is true in a set of worlds, and nonfalse in the other worlds [Hanna] |
| 11086 | Metaphysical necessity can be 'weak' (same as logical) and 'strong' (based on essences) [Hanna] |
| 11084 | Logical necessity is truth in all logically possible worlds, because of laws and concepts [Hanna] |
| 11085 | Nomological necessity is truth in all logically possible worlds with our laws [Hanna] |
| 11078 | Intuition is only outside the 'space of reasons' if all reasons are inferential [Hanna] |
| 11077 | Intuition includes apriority, clarity, modality, authority, fallibility and no inferences [Hanna] |
| 11080 | Intuition is more like memory, imagination or understanding, than like perception [Hanna] |
| 8850 | Agrippa's Trilemma: justification is infinite, or ends arbitrarily, or is circular [Agrippa, by Williams,M] |
| 1814 | Everything is perceived in relation to another thing (Mode 13) [Agrippa, by Diog. Laertius] |
| 11053 | Explanatory reduction is stronger than ontological reduction [Hanna] |
| 11081 | Imagination grasps abstracta, generates images, and has its own correctness conditions [Hanna] |
| 11082 | Should we take the 'depictivist' or the 'descriptivist/propositionalist' view of mental imagery? [Hanna] |
| 11068 | One tradition says talking is the essence of rationality; the other says the essence is logic [Hanna] |
| 11046 | Kantian principled rationality is recognition of a priori universal truths [Hanna] |
| 11048 | Humean Instrumental rationality is the capacity to seek contingent truths [Hanna] |
| 11067 | Rational animals have a normative concept of necessity [Hanna] |
| 11047 | Hegelian holistic rationality is the capacity to seek coherence [Hanna] |
| 11045 | Most psychologists are now cognitivists [Hanna] |