150 ideas
| 11300 | Agathon: good [PG] |
| 11301 | Aisthesis: perception, sensation, consciousness [PG] |
| 11302 | Aitia / aition: cause, explanation [PG] |
| 11303 | Akrasia: lack of control, weakness of will [PG] |
| 11304 | Aletheia: truth [PG] |
| 11305 | Anamnesis: recollection, remembrance [PG] |
| 11306 | Ananke: necessity [PG] |
| 11307 | Antikeimenon: object [PG] |
| 11375 | Apatheia: unemotional [PG] |
| 11308 | Apeiron: the unlimited, indefinite [PG] |
| 11376 | Aphairesis: taking away, abstraction [PG] |
| 11309 | Apodeixis: demonstration [PG] |
| 11310 | Aporia: puzzle, question, anomaly [PG] |
| 11311 | Arche: first principle, the basic [PG] |
| 11312 | Arete: virtue, excellence [PG] |
| 11313 | Chronismos: separation [PG] |
| 11314 | Diairesis: division [PG] |
| 11315 | Dialectic: dialectic, discussion [PG] |
| 11316 | Dianoia: intellection [cf. Noesis] [PG] |
| 11317 | Diaphora: difference [PG] |
| 11318 | Dikaiosune: moral goodness, justice [PG] |
| 11319 | Doxa: opinion, belief [PG] |
| 11320 | Dunamis: faculty, potentiality, capacity [PG] |
| 11321 | Eidos: form, idea [PG] |
| 11322 | Elenchos: elenchus, interrogation [PG] |
| 11323 | Empeiron: experience [PG] |
| 11324 | Energeia: employment, actuality, power? [PG] |
| 11325 | Enkrateia: control [PG] |
| 11326 | Entelecheia: entelechy, having an end [PG] |
| 11327 | Epagoge: induction, explanation [PG] |
| 11328 | Episteme: knowledge, understanding [PG] |
| 11329 | Epithumia: appetite [PG] |
| 11330 | Ergon: function [PG] |
| 11331 | Eristic: polemic, disputation [PG] |
| 11332 | Eros: love [PG] |
| 11333 | Eudaimonia: flourishing, happiness, fulfilment [PG] |
| 11334 | Genos: type, genus [PG] |
| 11335 | Hexis: state, habit [PG] |
| 11336 | Horismos: definition [PG] |
| 11337 | Hule: matter [PG] |
| 11338 | Hupokeimenon: subject, underlying thing [cf. Tode ti] [PG] |
| 11339 | Kalos / kalon: beauty, fineness, nobility [PG] |
| 11340 | Kath' hauto: in virtue of itself, essentially [PG] |
| 11341 | Kinesis: movement, process [PG] |
| 11342 | Kosmos: order, universe [PG] |
| 11343 | Logos: reason, account, word [PG] |
| 11344 | Meson: the mean [PG] |
| 11345 | Metechein: partaking, sharing [PG] |
| 11377 | Mimesis: imitation, fine art [PG] |
| 11346 | Morphe: form [PG] |
| 11347 | Noesis: intellection, rational thought [cf. Dianoia] [PG] |
| 11348 | Nomos: convention, law, custom [PG] |
| 11349 | Nous: intuition, intellect, understanding [PG] |
| 11350 | Orexis: desire [PG] |
| 11351 | Ousia: substance, (primary) being, [see 'Prote ousia'] [PG] |
| 11352 | Pathos: emotion, affection, property [PG] |
| 11353 | Phantasia: imagination [PG] |
| 11354 | Philia: friendship [PG] |
| 11355 | Philosophia: philosophy, love of wisdom [PG] |
| 11356 | Phronesis: prudence, practical reason, common sense [PG] |
| 11357 | Physis: nature [PG] |
| 11358 | Praxis: action, activity [PG] |
| 11359 | Prote ousia: primary being [PG] |
| 11360 | Psuche: mind, soul, life [PG] |
| 11361 | Sophia: wisdom [PG] |
| 11362 | Sophrosune: moderation, self-control [PG] |
| 11363 | Stoicheia: elements [PG] |
| 11364 | Sullogismos: deduction, syllogism [PG] |
| 11365 | Techne: skill, practical knowledge [PG] |
| 11366 | Telos: purpose, end [PG] |
| 11367 | Theoria: contemplation [PG] |
| 11368 | Theos: god [PG] |
| 11369 | Ti esti: what-something-is, essence [PG] |
| 11370 | Timoria: vengeance, punishment [PG] |
| 11371 | To ti en einai: essence, what-it-is-to-be [PG] |
| 11372 | To ti estin: essence [PG] |
| 11373 | Tode ti: this-such, subject of predication [cf. hupokeimenon] [PG] |
| 13439 | Venn Diagrams map three predicates into eight compartments, then look for the conclusion [Bostock] |
| 13421 | 'Disjunctive Normal Form' is ensuring that no conjunction has a disjunction within its scope [Bostock] |
| 13422 | 'Conjunctive Normal Form' is ensuring that no disjunction has a conjunction within its scope [Bostock] |
| 13355 | 'Disjunction' says that Γ,φ∨ψ|= iff Γ,φ|= and Γ,ψ|= [Bostock] |
| 13350 | 'Assumptions' says that a formula entails itself (φ|=φ) [Bostock] |
| 13351 | 'Thinning' allows that if premisses entail a conclusion, then adding further premisses makes no difference [Bostock] |
| 13356 | The 'conditional' is that Γ|=φ→ψ iff Γ,φ|=ψ [Bostock] |
| 13352 | 'Cutting' allows that if x is proved, and adding y then proves z, you can go straight to z [Bostock] |
| 13353 | 'Negation' says that Γ,¬φ|= iff Γ|=φ [Bostock] |
| 13354 | 'Conjunction' says that Γ|=φ∧ψ iff Γ|=φ and Γ|=ψ [Bostock] |
| 13610 | A logic with ¬ and → needs three axiom-schemas and one rule as foundation [Bostock] |
| 13846 | A 'free' logic can have empty names, and a 'universally free' logic can have empty domains [Bostock] |
| 13346 | Truth is the basic notion in classical logic [Bostock] |
| 13545 | Elementary logic cannot distinguish clearly between the finite and the infinite [Bostock] |
| 13822 | Fictional characters wreck elementary logic, as they have contradictions and no excluded middle [Bostock] |
| 13623 | The syntactic turnstile |- φ means 'there is a proof of φ' or 'φ is a theorem' [Bostock] |
| 13347 | Validity is a conclusion following for premises, even if there is no proof [Bostock] |
| 13348 | It seems more natural to express |= as 'therefore', rather than 'entails' [Bostock] |
| 13349 | Γ|=φ is 'entails'; Γ|= is 'is inconsistent'; |=φ is 'valid' [Bostock] |
| 13614 | MPP: 'If Γ|=φ and Γ|=φ→ψ then Γ|=ψ' (omit Γs for Detachment) [Bostock] |
| 13617 | MPP is a converse of Deduction: If Γ |- φ→ψ then Γ,φ|-ψ [Bostock] |
| 13799 | The sign '=' is a two-place predicate expressing that 'a is the same thing as b' (a=b) [Bostock] |
| 13800 | |= α=α and α=β |= φ(α/ξ ↔ φ(β/ξ) fix identity [Bostock] |
| 13803 | If we are to express that there at least two things, we need identity [Bostock] |
| 13357 | Truth-functors are usually held to be defined by their truth-tables [Bostock] |
| 13812 | A 'zero-place' function just has a single value, so it is a name [Bostock] |
| 13811 | A 'total' function ranges over the whole domain, a 'partial' function over appropriate inputs [Bostock] |
| 13360 | In logic, a name is just any expression which refers to a particular single object [Bostock] |
| 13361 | An expression is only a name if it succeeds in referring to a real object [Bostock] |
| 13814 | Definite desciptions resemble names, but can't actually be names, if they don't always refer [Bostock] |
| 13816 | Because of scope problems, definite descriptions are best treated as quantifiers [Bostock] |
| 13817 | Definite descriptions are usually treated like names, and are just like them if they uniquely refer [Bostock] |
| 13848 | We are only obliged to treat definite descriptions as non-names if only the former have scope [Bostock] |
| 13813 | Definite descriptions don't always pick out one thing, as in denials of existence, or errors [Bostock] |
| 13815 | Names do not have scope problems (e.g. in placing negation), but Russell's account does have that problem [Bostock] |
| 13438 | 'Prenex normal form' is all quantifiers at the beginning, out of the scope of truth-functors [Bostock] |
| 13818 | If we allow empty domains, we must allow empty names [Bostock] |
| 13801 | An 'informal proof' is in no particular system, and uses obvious steps and some ordinary English [Bostock] |
| 13619 | Quantification adds two axiom-schemas and a new rule [Bostock] |
| 13622 | Axiom systems from Frege, Russell, Church, Lukasiewicz, Tarski, Nicod, Kleene, Quine... [Bostock] |
| 13615 | 'Conditonalised' inferences point to the Deduction Theorem: If Γ,φ|-ψ then Γ|-φ→ψ [Bostock] |
| 13616 | The Deduction Theorem greatly simplifies the search for proof [Bostock] |
| 13620 | Proof by Assumptions can always be reduced to Proof by Axioms, using the Deduction Theorem [Bostock] |
| 13621 | The Deduction Theorem and Reductio can 'discharge' assumptions - they aren't needed for the new truth [Bostock] |
| 13753 | Natural deduction takes proof from assumptions (with its rules) as basic, and axioms play no part [Bostock] |
| 13755 | Excluded middle is an introduction rule for negation, and ex falso quodlibet will eliminate it [Bostock] |
| 13758 | In natural deduction we work from the premisses and the conclusion, hoping to meet in the middle [Bostock] |
| 13754 | Natural deduction rules for → are the Deduction Theorem (→I) and Modus Ponens (→E) [Bostock] |
| 13611 | Tableau proofs use reduction - seeking an impossible consequence from an assumption [Bostock] |
| 13613 | A completed open branch gives an interpretation which verifies those formulae [Bostock] |
| 13612 | Non-branching rules add lines, and branching rules need a split; a branch with a contradiction is 'closed' [Bostock] |
| 13761 | In a tableau proof no sequence is established until the final branch is closed; hypotheses are explored [Bostock] |
| 13757 | Unlike natural deduction, semantic tableaux have recipes for proving things [Bostock] |
| 13756 | A tree proof becomes too broad if its only rule is Modus Ponens [Bostock] |
| 13762 | Tableau rules are all elimination rules, gradually shortening formulae [Bostock] |
| 13759 | Each line of a sequent calculus is a conclusion of previous lines, each one explicitly recorded [Bostock] |
| 13760 | A sequent calculus is good for comparing proof systems [Bostock] |
| 13364 | Interpretation by assigning objects to names, or assigning them to variables first [Bostock, by PG] |
| 13821 | Extensionality is built into ordinary logic semantics; names have objects, predicates have sets of objects [Bostock] |
| 13362 | If an object has two names, truth is undisturbed if the names are swapped; this is Extensionality [Bostock] |
| 13541 | For 'negation-consistent', there is never |-(S)φ and |-(S)¬φ [Bostock] |
| 13542 | A proof-system is 'absolutely consistent' iff we don't have |-(S)φ for every formula [Bostock] |
| 13540 | A set of formulae is 'inconsistent' when there is no interpretation which can make them all true [Bostock] |
| 13544 | Inconsistency or entailment just from functors and quantifiers is finitely based, if compact [Bostock] |
| 13618 | Compactness means an infinity of sequents on the left will add nothing new [Bostock] |
| 13358 | Ordinary or mathematical induction assumes for the first, then always for the next, and hence for all [Bostock] |
| 13359 | Complete induction assumes for all numbers less than n, then also for n, and hence for all numbers [Bostock] |
| 13543 | A relation is not reflexive, just because it is transitive and symmetrical [Bostock] |
| 13802 | Relations can be one-many (at most one on the left) or many-one (at most one on the right) [Bostock] |
| 12155 | Statements of 'relative identity' are really statements of resemblance [Perry] |
| 13847 | If non-existent things are self-identical, they are just one thing - so call it the 'null object' [Bostock] |
| 13820 | The idea that anything which can be proved is necessary has a problem with empty names [Bostock] |
| 13363 | A (modern) predicate is the result of leaving a gap for the name in a sentence [Bostock] |