108 ideas
| 11300 | Agathon: good [PG] |
| Full Idea: Agathon: good, the highest good | |
| From: PG (Db (lexicon) [c.1001 BCE], 01) |
| 11301 | Aisthesis: perception, sensation, consciousness [PG] |
| Full Idea: Aisthesis: perception, sensation, consciousness | |
| From: PG (Db (lexicon) [c.1001 BCE], 02) |
| 11302 | Aitia / aition: cause, explanation [PG] |
| Full Idea: Aitia / aition: cause, explanation | |
| From: PG (Db (lexicon) [c.1001 BCE], 03) | |
| A reaction: The consensus is that 'explanation' is the better translation, and hence that the famous Four Causes (in 'Physics') must really be understood as the Four Modes of Explanation. They then make far more sense. |
| 11303 | Akrasia: lack of control, weakness of will [PG] |
| Full Idea: Akrasia: lack of control, weakness of will | |
| From: PG (Db (lexicon) [c.1001 BCE], 04) | |
| A reaction: The whole Greek debate (and modern debate, I would say) makes much more sense if we stick to 'lack of control' as the translation, and forget about weakness of will - and certainly give up 'incontinence' as a translation. |
| 11304 | Aletheia: truth [PG] |
| Full Idea: Aletheia: truth | |
| From: PG (Db (lexicon) [c.1001 BCE], 05) |
| 11305 | Anamnesis: recollection, remembrance [PG] |
| Full Idea: Anamnesis: recollection, remembrance | |
| From: PG (Db (lexicon) [c.1001 BCE], 06) | |
| A reaction: This is used for Plato's doctrine that we recollect past lives. |
| 11306 | Ananke: necessity [PG] |
| Full Idea: Ananke: necessity | |
| From: PG (Db (lexicon) [c.1001 BCE], 07) |
| 11307 | Antikeimenon: object [PG] |
| Full Idea: Antikeimenon: object | |
| From: PG (Db (lexicon) [c.1001 BCE], 08) |
| 11375 | Apatheia: unemotional [PG] |
| Full Idea: Apatheia: lack of involvement, unemotional | |
| From: PG (Db (lexicon) [c.1001 BCE], 09) |
| 11308 | Apeiron: the unlimited, indefinite [PG] |
| Full Idea: Apeiron: the unlimited, indefinite | |
| From: PG (Db (lexicon) [c.1001 BCE], 10) | |
| A reaction: Key term in the philosophy of Anaximander, the one unknowable underlying element. |
| 11376 | Aphairesis: taking away, abstraction [PG] |
| Full Idea: Aphairesis: taking away, abstraction | |
| From: PG (Db (lexicon) [c.1001 BCE], 11) |
| 11309 | Apodeixis: demonstration [PG] |
| Full Idea: Apodeixis: demonstration, proof | |
| From: PG (Db (lexicon) [c.1001 BCE], 12) |
| 11310 | Aporia: puzzle, question, anomaly [PG] |
| Full Idea: Aporia: puzzle, question, anomaly | |
| From: PG (Db (lexicon) [c.1001 BCE], 13) |
| 11311 | Arche: first principle, the basic [PG] |
| Full Idea: Arché: first principle, the basic | |
| From: PG (Db (lexicon) [c.1001 BCE], 14) | |
| A reaction: Interchangeable with 'aitia' by Aristotle. The first principle and the cause are almost identical. |
| 11312 | Arete: virtue, excellence [PG] |
| Full Idea: Areté: virtue, excellence | |
| From: PG (Db (lexicon) [c.1001 BCE], 15) | |
| A reaction: The word hovers between moral excellence and being good at what you do. Annas defends the older translation as 'virtue', rather than the modern 'excellence'. |
| 11313 | Chronismos: separation [PG] |
| Full Idea: Chronismos: separation | |
| From: PG (Db (lexicon) [c.1001 BCE], 16) |
| 11314 | Diairesis: division [PG] |
| Full Idea: Diairesis: division, distinction | |
| From: PG (Db (lexicon) [c.1001 BCE], 17) |
| 11315 | Dialectic: dialectic, discussion [PG] |
| Full Idea: Dialectic: dialectic, discussion | |
| From: PG (Db (lexicon) [c.1001 BCE], 18) |
| 11316 | Dianoia: intellection [cf. Noesis] [PG] |
| Full Idea: Dianoia: intellection, understanding [cf. Noesis] | |
| From: PG (Db (lexicon) [c.1001 BCE], 21) |
| 11317 | Diaphora: difference [PG] |
| Full Idea: Diaphora: difference | |
| From: PG (Db (lexicon) [c.1001 BCE], 22) |
| 11318 | Dikaiosune: moral goodness, justice [PG] |
| Full Idea: Dikaiosune: moral goodness, justice | |
| From: PG (Db (lexicon) [c.1001 BCE], 23) | |
| A reaction: Usually translated as 'justice' in 'Republic', but it is a general term of moral approbation, not like the modern political and legal notion of 'justice'. 'Justice' actually seems to be bad translation. |
| 11319 | Doxa: opinion, belief [PG] |
| Full Idea: Doxa: opinion, belief, judgement | |
| From: PG (Db (lexicon) [c.1001 BCE], 24) |
| 11320 | Dunamis: faculty, potentiality, capacity [PG] |
| Full Idea: Dunamis: faculty, potentiality, capacity | |
| From: PG (Db (lexicon) [c.1001 BCE], 25) |
| 11321 | Eidos: form, idea [PG] |
| Full Idea: Eidos: form, idea | |
| From: PG (Db (lexicon) [c.1001 BCE], 26) | |
| A reaction: In Plato it is the word best translated as 'Form' (Theory of...); in Aritotle's 'Categories' it designates the species, and in 'Metaphysics' it ends up naming the structural form of the species (and hence the essence) [Wedin p.120] |
| 11322 | Elenchos: elenchus, interrogation [PG] |
| Full Idea: Elenchos: elenchus, interrogation | |
| From: PG (Db (lexicon) [c.1001 BCE], 27) |
| 11323 | Empeiron: experience [PG] |
| Full Idea: Empeiron: experience | |
| From: PG (Db (lexicon) [c.1001 BCE], 28) |
| 11324 | Energeia: employment, actuality, power? [PG] |
| Full Idea: Energeia: employment, actuality, power? | |
| From: PG (Db (lexicon) [c.1001 BCE], 31) |
| 11325 | Enkrateia: control [PG] |
| Full Idea: Enkrateia: control | |
| From: PG (Db (lexicon) [c.1001 BCE], 32) | |
| A reaction: See 'akrasia', of which this is the opposite. The enkratic person is controlled. |
| 11326 | Entelecheia: entelechy, having an end [PG] |
| Full Idea: Entelecheia: entelechy, having an end | |
| From: PG (Db (lexicon) [c.1001 BCE], 33) |
| 11327 | Epagoge: induction, explanation [PG] |
| Full Idea: Epagoge: induction, explanation, leading on | |
| From: PG (Db (lexicon) [c.1001 BCE], 34) |
| 11328 | Episteme: knowledge, understanding [PG] |
| Full Idea: Episteme: knowledge, understanding | |
| From: PG (Db (lexicon) [c.1001 BCE], 35) | |
| A reaction: Note that 'episteme' can form a plural in Greek, but we can't say 'knowledges', so we have to say 'branches of knowledge', or 'sciences'. |
| 11329 | Epithumia: appetite [PG] |
| Full Idea: Epithumia: appetite | |
| From: PG (Db (lexicon) [c.1001 BCE], 36) |
| 11330 | Ergon: function [PG] |
| Full Idea: Ergon: function, work | |
| From: PG (Db (lexicon) [c.1001 BCE], 37) |
| 11331 | Eristic: polemic, disputation [PG] |
| Full Idea: Eristic: polemic, disputation | |
| From: PG (Db (lexicon) [c.1001 BCE], 38) | |
| A reaction: This is confrontational argument, rather than the subtle co-operative dialogue of dialectic. British law courts and the House of Commons are founded on eristic, rather than on dialectic. Could there be a dialectical elected assembly? |
| 11332 | Eros: love [PG] |
| Full Idea: Eros: love, desire | |
| From: PG (Db (lexicon) [c.1001 BCE], 41) |
| 11333 | Eudaimonia: flourishing, happiness, fulfilment [PG] |
| Full Idea: Eudaimonia: flourishing, happiness, fulfilment | |
| From: PG (Db (lexicon) [c.1001 BCE], 42) | |
| A reaction: Some people defend 'happiness' as the translation, but that seems to me wildly misleading, since eudaimonia is something like life going well, and certainly isn't a psychological state - and definitely not pleasure. |
| 11334 | Genos: type, genus [PG] |
| Full Idea: Genos: type, genus, kind | |
| From: PG (Db (lexicon) [c.1001 BCE], 43) |
| 11335 | Hexis: state, habit [PG] |
| Full Idea: Hexis: state, habit | |
| From: PG (Db (lexicon) [c.1001 BCE], 44) |
| 11336 | Horismos: definition [PG] |
| Full Idea: Horismos: definition | |
| From: PG (Db (lexicon) [c.1001 BCE], 45) |
| 11337 | Hule: matter [PG] |
| Full Idea: Hule: matter | |
| From: PG (Db (lexicon) [c.1001 BCE], 46) | |
| A reaction: The first half of the 'hylomorphism' of Aristotle. See 'morphe'! |
| 11338 | Hupokeimenon: subject, underlying thing [cf. Tode ti] [PG] |
| Full Idea: Hupokeimenon: subject, underlying thing, substratum [cf. Tode ti] | |
| From: PG (Db (lexicon) [c.1001 BCE], 47) | |
| A reaction: Literally 'that which lies under'. Latin version is 'substratum'. In Aristotle it is the problem, of explaining what lies under. It is not the theory that there is some entity called a 'substratum'. |
| 11339 | Kalos / kalon: beauty, fineness, nobility [PG] |
| Full Idea: Kalos / kalon: beauty, fineness, nobility | |
| From: PG (Db (lexicon) [c.1001 BCE], 48) | |
| A reaction: A revealing Greek word, which is not only our rather pure notion of 'beauty', but also seems to mean something like wow!, and (very suggestive, this) applies as much to actions as to objects. |
| 11340 | Kath' hauto: in virtue of itself, essentially [PG] |
| Full Idea: Kath' hauto: in virtue of itself, essentially | |
| From: PG (Db (lexicon) [c.1001 BCE], 51) |
| 11341 | Kinesis: movement, process [PG] |
| Full Idea: Kinesis: movement, process, change | |
| From: PG (Db (lexicon) [c.1001 BCE], 52) |
| 11342 | Kosmos: order, universe [PG] |
| Full Idea: Kosmos: order, universe | |
| From: PG (Db (lexicon) [c.1001 BCE], 53) |
| 11343 | Logos: reason, account, word [PG] |
| Full Idea: Logos: reason, account, word | |
| From: PG (Db (lexicon) [c.1001 BCE], 54) |
| 11344 | Meson: the mean [PG] |
| Full Idea: Meson: the mean | |
| From: PG (Db (lexicon) [c.1001 BCE], 55) | |
| A reaction: This is not the 'average', and hence not some theoretical mid-point. I would call it the 'appropriate compromise', remembering that an extreme may be appropriate in certain circumstances. |
| 11345 | Metechein: partaking, sharing [PG] |
| Full Idea: Metechein: partaking, sharing | |
| From: PG (Db (lexicon) [c.1001 BCE], 56) | |
| A reaction: The key word in Plato for the difficult question of the relationships between the Forms and the particulars. The latter 'partake' of the former. Hm. Compare modern 'instantiation', which strikes me as being equally problematic. |
| 11377 | Mimesis: imitation, fine art [PG] |
| Full Idea: Mimesis: imitation, fine art | |
| From: PG (Db (lexicon) [c.1001 BCE], 57) |
| 11346 | Morphe: form [PG] |
| Full Idea: Morphe: form | |
| From: PG (Db (lexicon) [c.1001 BCE], 58) |
| 11347 | Noesis: intellection, rational thought [cf. Dianoia] [PG] |
| Full Idea: Noesis: intellection, rational thought [cf. Dianoia] | |
| From: PG (Db (lexicon) [c.1001 BCE], 59) |
| 11348 | Nomos: convention, law, custom [PG] |
| Full Idea: Nomos: convention, law, custom | |
| From: PG (Db (lexicon) [c.1001 BCE], 61) |
| 11349 | Nous: intuition, intellect, understanding [PG] |
| Full Idea: Nous: intuition, intellect | |
| From: PG (Db (lexicon) [c.1001 BCE], 62) | |
| A reaction: There is a condensed discussion of 'nous' in Aristotle's Posterior Analytics B.19 |
| 11350 | Orexis: desire [PG] |
| Full Idea: Orexis: desire | |
| From: PG (Db (lexicon) [c.1001 BCE], 63) |
| 11351 | Ousia: substance, (primary) being, [see 'Prote ousia'] [PG] |
| Full Idea: Ousia: substance, (primary) being [see 'Prote ousia'] | |
| From: PG (Db (lexicon) [c.1001 BCE], 64) | |
| A reaction: It is based on the verb 'to be'. Latin therefore translated it as 'essentia' (esse: to be), and we have ended up translating it as 'essence', but this is wrong! 'Being' is the best translation, and 'substance' is OK. It is the problem, not the answer. |
| 11352 | Pathos: emotion, affection, property [PG] |
| Full Idea: Pathos: emotion, affection, property | |
| From: PG (Db (lexicon) [c.1001 BCE], 65) |
| 11353 | Phantasia: imagination [PG] |
| Full Idea: Phantasia: imagination | |
| From: PG (Db (lexicon) [c.1001 BCE], 66) |
| 11354 | Philia: friendship [PG] |
| Full Idea: Philia: friendship | |
| From: PG (Db (lexicon) [c.1001 BCE], 67) |
| 11355 | Philosophia: philosophy, love of wisdom [PG] |
| Full Idea: Philosophia: philosophy, love of wisdom | |
| From: PG (Db (lexicon) [c.1001 BCE], 68) | |
| A reaction: The point of the word is its claim only to love wisdom, and not actually to be wise. |
| 11356 | Phronesis: prudence, practical reason, common sense [PG] |
| Full Idea: Phronesis: prudence, practical reason, common sense | |
| From: PG (Db (lexicon) [c.1001 BCE], 71) | |
| A reaction: None of the experts use my own translation, which is 'common sense', but that seems to me to perfectly fit all of Aristotle's discussions of the word in 'Ethics'. 'Prudence' seems a daft translation in modern English. |
| 11357 | Physis: nature [PG] |
| Full Idea: Physis: nature | |
| From: PG (Db (lexicon) [c.1001 BCE], 72) |
| 11358 | Praxis: action, activity [PG] |
| Full Idea: Praxis: action, activity | |
| From: PG (Db (lexicon) [c.1001 BCE], 73) |
| 11359 | Prote ousia: primary being [PG] |
| Full Idea: Prote ousia: primary being | |
| From: PG (Db (lexicon) [c.1001 BCE], 74) | |
| A reaction: The main topic of investigation in Aristotle's 'Metaphysics'. 'Ousia' is the central problem of the text, NOT the answer to the problem. |
| 11360 | Psuche: mind, soul, life [PG] |
| Full Idea: Psuche: mind, soul, life | |
| From: PG (Db (lexicon) [c.1001 BCE], 75) | |
| A reaction: The interesting thing about this is that we have tended to translate it as 'soul', but Aristotle says plants have it, and not merely conscious beings. It is something like the 'form' of a living thing, but then 'form' is a misleading translation too. |
| 11361 | Sophia: wisdom [PG] |
| Full Idea: Sophia: wisdom | |
| From: PG (Db (lexicon) [c.1001 BCE], 76) |
| 11362 | Sophrosune: moderation, self-control [PG] |
| Full Idea: Sophrosune: moderation, self-control | |
| From: PG (Db (lexicon) [c.1001 BCE], 77) |
| 11363 | Stoicheia: elements [PG] |
| Full Idea: Stoicheia: elements | |
| From: PG (Db (lexicon) [c.1001 BCE], 78) |
| 11364 | Sullogismos: deduction, syllogism [PG] |
| Full Idea: Sullogismos: deduction, syllogism | |
| From: PG (Db (lexicon) [c.1001 BCE], 81) |
| 11365 | Techne: skill, practical knowledge [PG] |
| Full Idea: Techne: skill, practical knowledge | |
| From: PG (Db (lexicon) [c.1001 BCE], 82) |
| 11366 | Telos: purpose, end [PG] |
| Full Idea: Telos: purpose, end | |
| From: PG (Db (lexicon) [c.1001 BCE], 83) |
| 11367 | Theoria: contemplation [PG] |
| Full Idea: Theoria: contemplation | |
| From: PG (Db (lexicon) [c.1001 BCE], 84) |
| 11368 | Theos: god [PG] |
| Full Idea: Theos: god | |
| From: PG (Db (lexicon) [c.1001 BCE], 85) |
| 11369 | Ti esti: what-something-is, essence [PG] |
| Full Idea: Ti esti: the what-something-is, essence, whatness | |
| From: PG (Db (lexicon) [c.1001 BCE], 86) |
| 11370 | Timoria: vengeance, punishment [PG] |
| Full Idea: Timoria: vengeance, punishment | |
| From: PG (Db (lexicon) [c.1001 BCE], 87) |
| 11371 | To ti en einai: essence, what-it-is-to-be [PG] |
| Full Idea: To ti en einai: essence, what-it-is-to-be | |
| From: PG (Db (lexicon) [c.1001 BCE], 88) | |
| A reaction: This is Aristotle's main term for what we would now call the 'essence'. It is still not a theory of essence, merely an identification of the target. 'Form' is the nearest we get to his actual theory. |
| 11372 | To ti estin: essence [PG] |
| Full Idea: To ti estin: essence | |
| From: PG (Db (lexicon) [c.1001 BCE], 91) |
| 11373 | Tode ti: this-such, subject of predication [cf. hupokeimenon] [PG] |
| Full Idea: Tode ti: this-something, subject of predication, thisness [cf. hupokeimenon] | |
| From: PG (Db (lexicon) [c.1001 BCE], 92) |
| 9724 | Until the 1960s the only semantics was truth-tables [Enderton] |
| Full Idea: Until the 1960s standard truth-table semantics were the only ones that there were. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.10.1) | |
| A reaction: The 1960s presumably marked the advent of possible worlds. |
| 9703 | 'dom R' indicates the 'domain' of objects having a relation [Enderton] |
| Full Idea: 'dom R' indicates the 'domain' of a relation, that is, the set of all objects that are members of ordered pairs and that have that relation. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9705 | 'fld R' indicates the 'field' of all objects in the relation [Enderton] |
| Full Idea: 'fld R' indicates the 'field' of a relation, that is, the set of all objects that are members of ordered pairs on either side of the relation. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9704 | 'ran R' indicates the 'range' of objects being related to [Enderton] |
| Full Idea: 'ran R' indicates the 'range' of a relation, that is, the set of all objects that are members of ordered pairs and that are related to by the first objects. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9710 | We write F:A→B to indicate that A maps into B (the output of F on A is in B) [Enderton] |
| Full Idea: We write F : A → B to indicate that A maps into B, that is, the domain of relating things is set A, and the things related to are all in B. If we add that F = B, then A maps 'onto' B. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9707 | 'F(x)' is the unique value which F assumes for a value of x [Enderton] |
|
Full Idea:
F(x) is a 'function', which indicates the unique value which y takes in |
|
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9712 | A relation is 'symmetric' on a set if every ordered pair has the relation in both directions [Enderton] |
| Full Idea: A relation is 'symmetric' on a set if every ordered pair in the set has the relation in both directions. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9713 | A relation is 'transitive' if it can be carried over from two ordered pairs to a third [Enderton] |
| Full Idea: A relation is 'transitive' on a set if the relation can be carried over from two ordered pairs to a third. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9699 | The 'powerset' of a set is all the subsets of a given set [Enderton] |
| Full Idea: The 'powerset' of a set is all the subsets of a given set. Thus: PA = {x : x ⊆ A}. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9700 | Two sets are 'disjoint' iff their intersection is empty [Enderton] |
| Full Idea: Two sets are 'disjoint' iff their intersection is empty (i.e. they have no members in common). | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9702 | A 'domain' of a relation is the set of members of ordered pairs in the relation [Enderton] |
| Full Idea: The 'domain' of a relation is the set of all objects that are members of ordered pairs that are members of the relation. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9701 | A 'relation' is a set of ordered pairs [Enderton] |
| Full Idea: A 'relation' is a set of ordered pairs. The ordering relation on the numbers 0-3 is captured by - in fact it is - the set of ordered pairs {<0,1>,<0,2>,<0,3>,<1,2>,<1,3>,<2,3>}. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) | |
| A reaction: This can't quite be a definition of order among numbers, since it relies on the notion of a 'ordered' pair. |
| 9706 | A 'function' is a relation in which each object is related to just one other object [Enderton] |
| Full Idea: A 'function' is a relation which is single-valued. That is, for each object, there is only one object in the function set to which that object is related. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9708 | A function 'maps A into B' if the relating things are set A, and the things related to are all in B [Enderton] |
| Full Idea: A function 'maps A into B' if the domain of relating things is set A, and the things related to are all in B. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9709 | A function 'maps A onto B' if the relating things are set A, and the things related to are set B [Enderton] |
| Full Idea: A function 'maps A onto B' if the domain of relating things is set A, and the things related to are set B. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9711 | A relation is 'reflexive' on a set if every member bears the relation to itself [Enderton] |
| Full Idea: A relation is 'reflexive' on a set if every member of the set bears the relation to itself. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9714 | A relation satisfies 'trichotomy' if all pairs are either relations, or contain identical objects [Enderton] |
| Full Idea: A relation satisfies 'trichotomy' on a set if every ordered pair is related (in either direction), or the objects are identical. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9717 | A set is 'dominated' by another if a one-to-one function maps the first set into a subset of the second [Enderton] |
| Full Idea: A set is 'dominated' by another if a one-to-one function maps the first set into a subset of the second. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9715 | An 'equivalence relation' is a reflexive, symmetric and transitive binary relation [Enderton] |
| Full Idea: An 'equivalence relation' is a binary relation which is reflexive, and symmetric, and transitive. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9716 | We 'partition' a set into distinct subsets, according to each relation on its objects [Enderton] |
| Full Idea: Equivalence classes will 'partition' a set. That is, it will divide it into distinct subsets, according to each relation on the set. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], Ch.0) |
| 9722 | Inference not from content, but from the fact that it was said, is 'conversational implicature' [Enderton] |
| Full Idea: The process is dubbed 'conversational implicature' when the inference is not from the content of what has been said, but from the fact that it has been said. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.7.3) |
| 9718 | Validity is either semantic (what preserves truth), or proof-theoretic (following procedures) [Enderton] |
| Full Idea: The point of logic is to give an account of the notion of validity,..in two standard ways: the semantic way says that a valid inference preserves truth (symbol |=), and the proof-theoretic way is defined in terms of purely formal procedures (symbol |-). | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.1.3..) | |
| A reaction: This division can be mirrored in mathematics, where it is either to do with counting or theorising about things in the physical world, or following sets of rules from axioms. Language can discuss reality, or play word-games. |
| 9721 | A logical truth or tautology is a logical consequence of the empty set [Enderton] |
| Full Idea: A is a logical truth (tautology) (|= A) iff it is a semantic consequence of the empty set of premises (φ |= A), that is, every interpretation makes A true. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.3.4) | |
| A reaction: So the final column of every line of the truth table will be T. |
| 9994 | A truth assignment to the components of a wff 'satisfy' it if the wff is then True [Enderton] |
| Full Idea: A truth assignment 'satisfies' a formula, or set of formulae, if it evaluates as True when all of its components have been assigned truth values. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.2) | |
| A reaction: [very roughly what Enderton says!] The concept becomes most significant when a large set of wff's is pronounced 'satisfied' after a truth assignment leads to them all being true. |
| 9719 | A proof theory is 'sound' if its valid inferences entail semantic validity [Enderton] |
| Full Idea: If every proof-theoretically valid inference is semantically valid (so that |- entails |=), the proof theory is said to be 'sound'. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.1.7) |
| 9720 | A proof theory is 'complete' if semantically valid inferences entail proof-theoretic validity [Enderton] |
| Full Idea: If every semantically valid inference is proof-theoretically valid (so that |= entails |-), the proof-theory is said to be 'complete'. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.1.7) |
| 9995 | Proof in finite subsets is sufficient for proof in an infinite set [Enderton] |
| Full Idea: If a wff is tautologically implied by a set of wff's, it is implied by a finite subset of them; and if every finite subset is satisfiable, then so is the whole set of wff's. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 2.5) | |
| A reaction: [Enderton's account is more symbolic] He adds that this also applies to models. It is a 'theorem' because it can be proved. It is a major theorem in logic, because it brings the infinite under control, and who doesn't want that? |
| 9996 | Expressions are 'decidable' if inclusion in them (or not) can be proved [Enderton] |
| Full Idea: A set of expressions is 'decidable' iff there exists an effective procedure (qv) that, given some expression, will decide whether or not the expression is included in the set (i.e. doesn't contradict it). | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.7) | |
| A reaction: This is obviously a highly desirable feature for a really reliable system of expressions to possess. All finite sets are decidable, but some infinite sets are not. |
| 9997 | For a reasonable language, the set of valid wff's can always be enumerated [Enderton] |
| Full Idea: The Enumerability Theorem says that for a reasonable language, the set of valid wff's can be effectively enumerated. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 2.5) | |
| A reaction: There are criteria for what makes a 'reasonable' language (probably specified to ensure enumerability!). Predicates and functions must be decidable, and the language must be finite. |
| 9723 | Sentences with 'if' are only conditionals if they can read as A-implies-B [Enderton] |
| Full Idea: Not all sentences using 'if' are conditionals. Consider 'if you want a banana, there is one in the kitchen'. The rough test is that a conditional can be rewritten as 'that A implies that B'. | |
| From: Herbert B. Enderton (A Mathematical Introduction to Logic (2nd) [2001], 1.6.4) |
| 468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
| Full Idea: In singing and playing the lyre, a boy will be likely to reveal not only courage and moderation, but also justice. | |
| From: Damon (fragments/reports [c.460 BCE], B4), quoted by (who?) - where? |