135 ideas
15357 | Philosophy is the most general intellectual discipline [Horsten] |
20910 | Everything happens necessarily, and for a reason [Democritus] |
15352 | A definition should allow the defined term to be eliminated [Horsten] |
10882 | Predicative definitions only refer to entities outside the defined collection [Horsten] |
15324 | Semantic theories of truth seek models; axiomatic (syntactic) theories seek logical principles [Horsten] |
15323 | Truth is a property, because the truth predicate has an extension [Horsten] |
15374 | Truth has no 'nature', but we should try to describe its behaviour in inferences [Horsten] |
15348 | Propositions have sentence-like structures, so it matters little which bears the truth [Horsten] |
15333 | Modern correspondence is said to be with the facts, not with true propositions [Horsten] |
15337 | The correspondence 'theory' is too vague - about both 'correspondence' and 'facts' [Horsten] |
15334 | The coherence theory allows multiple coherent wholes, which could contradict one another [Horsten] |
15336 | The pragmatic theory of truth is relative; useful for group A can be useless for group B [Horsten] |
15354 | Tarski's hierarchy lacks uniform truth, and depends on contingent factors [Horsten] |
15340 | Tarski Bi-conditional: if you'll assert φ you'll assert φ-is-true - and also vice versa [Horsten] |
15345 | Semantic theories have a regress problem in describing truth in the languages for the models [Horsten] |
15373 | Axiomatic approaches avoid limiting definitions to avoid the truth predicate, and limited sizes of models [Horsten] |
15346 | Axiomatic approaches to truth avoid the regress problem of semantic theories [Horsten] |
15371 | An axiomatic theory needs to be of maximal strength, while being natural and sound [Horsten] |
15332 | 'Reflexive' truth theories allow iterations (it is T that it is T that p) [Horsten] |
15361 | A good theory of truth must be compositional (as well as deriving biconditionals) [Horsten] |
15350 | The Naïve Theory takes the bi-conditionals as axioms, but it is inconsistent, and allows the Liar [Horsten] |
15351 | Axiomatic theories take truth as primitive, and propose some laws of truth as axioms [Horsten] |
15367 | By adding truth to Peano Arithmetic we increase its power, so truth has mathematical content! [Horsten] |
15330 | Friedman-Sheard theory keeps classical logic and aims for maximum strength [Horsten] |
15331 | Kripke-Feferman has truth gaps, instead of classical logic, and aims for maximum strength [Horsten] |
15325 | Inferential deflationism says truth has no essence because no unrestricted logic governs the concept [Horsten] |
15344 | Deflationism skips definitions and models, and offers just accounts of basic laws of truth [Horsten] |
15356 | Deflationism concerns the nature and role of truth, but not its laws [Horsten] |
15368 | This deflationary account says truth has a role in generality, and in inference [Horsten] |
15358 | Deflationism says truth isn't a topic on its own - it just concerns what is true [Horsten] |
15359 | Deflation: instead of asserting a sentence, we can treat it as an object with the truth-property [Horsten] |
15329 | Nonclassical may accept T/F but deny applicability, or it may deny just T or F as well [Horsten] |
10482 | The logic of ZF is classical first-order predicate logic with identity [Boolos] |
10492 | A few axioms of set theory 'force themselves on us', but most of them don't [Boolos] |
18192 | Do the Replacement Axioms exceed the iterative conception of sets? [Boolos, by Maddy] |
7785 | The use of plurals doesn't commit us to sets; there do not exist individuals and collections [Boolos] |
10485 | Naïve sets are inconsistent: there is no set for things that do not belong to themselves [Boolos] |
10484 | The iterative conception says sets are formed at stages; some are 'earlier', and must be formed first [Boolos] |
13547 | Limitation of Size is weak (Fs only collect is something the same size does) or strong (fewer Fs than objects) [Boolos, by Potter] |
10699 | Does a bowl of Cheerios contain all its sets and subsets? [Boolos] |
15326 | Doubt is thrown on classical logic by the way it so easily produces the liar paradox [Horsten] |
14249 | Boolos reinterprets second-order logic as plural logic [Boolos, by Oliver/Smiley] |
10225 | Monadic second-order logic might be understood in terms of plural quantifiers [Boolos, by Shapiro] |
10830 | Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos] |
10736 | Boolos showed how plural quantifiers can interpret monadic second-order logic [Boolos, by Linnebo] |
10780 | Any sentence of monadic second-order logic can be translated into plural first-order logic [Boolos, by Linnebo] |
15341 | Deduction Theorem: ψ only derivable from φ iff φ→ψ are axioms [Horsten] |
10829 | A sentence can't be a truth of logic if it asserts the existence of certain sets [Boolos] |
10697 | Identity is clearly a logical concept, and greatly enhances predicate calculus [Boolos] |
15328 | A theory is 'non-conservative' if it facilitates new mathematical proofs [Horsten] |
10832 | '∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos] |
13671 | Second-order quantifiers are just like plural quantifiers in ordinary language, with no extra ontology [Boolos, by Shapiro] |
10267 | We should understand second-order existential quantifiers as plural quantifiers [Boolos, by Shapiro] |
10698 | Plural forms have no more ontological commitment than to first-order objects [Boolos] |
7806 | Boolos invented plural quantification [Boolos, by Benardete,JA] |
15349 | It is easier to imagine truth-value gaps (for the Liar, say) than for truth-value gluts (both T and F) [Horsten] |
15366 | Satisfaction is a primitive notion, and very liable to semantical paradoxes [Horsten] |
10884 | A theory is 'categorical' if it has just one model up to isomorphism [Horsten] |
10834 | Weak completeness: if it is valid, it is provable. Strong: it is provable from a set of sentences [Boolos] |
15353 | The first incompleteness theorem means that consistency does not entail soundness [Horsten] |
13841 | Why should compactness be definitive of logic? [Boolos, by Hacking] |
15355 | Strengthened Liar: 'this sentence is not true in any context' - in no context can this be evaluated [Horsten] |
15364 | English expressions are denumerably infinite, but reals are nondenumerable, so many are unnameable [Horsten] |
16146 | Two can't be a self-contained unit, because it would need to be one to do that [Democritus, by Aristotle] |
10491 | Infinite natural numbers is as obvious as infinite sentences in English [Boolos] |
10483 | Mathematics and science do not require very high orders of infinity [Boolos] |
10885 | Computer proofs don't provide explanations [Horsten] |
10833 | Many concepts can only be expressed by second-order logic [Boolos] |
10881 | The concept of 'ordinal number' is set-theoretic, not arithmetical [Horsten] |
15360 | ZFC showed that the concept of set is mathematical, not logical, because of its existence claims [Horsten] |
15369 | Set theory is substantial over first-order arithmetic, because it enables new proofs [Horsten] |
10490 | Mathematics isn't surprising, given that we experience many objects as abstract [Boolos] |
15370 | Predicativism says mathematical definitions must not include the thing being defined [Horsten] |
20901 | True Being only occurs when it is completely full, with atoms and no void [Democritus, by Aristotle] |
20902 | Being does not exist more than non-being [Democritus, by Aristotle] |
20904 | The non-existent exists as much as the existent, because it has causal powers [Democritus] |
20903 | The only distinctions are Configuration (shape), Disposition (order) and Turning (position) [Democritus, by Aristotle] |
20893 | Nothing comes from non-existence, or passes into it [Democritus, by Diog. Laertius] |
15338 | We may believe in atomic facts, but surely not complex disjunctive ones? [Horsten] |
15363 | In the supervaluationist account, disjunctions are not determined by their disjuncts [Horsten] |
15362 | If 'Italy is large' lacks truth, so must 'Italy is not large'; but classical logic says it's large or it isn't [Horsten] |
10700 | First- and second-order quantifiers are two ways of referring to the same things [Boolos] |
20896 | It is not possible to know what sort each thing is [Democritus] |
10488 | It is lunacy to think we only see ink-marks, and not word-types [Boolos] |
10487 | I am a fan of abstract objects, and confident of their existence [Boolos] |
10489 | We deal with abstract objects all the time: software, poems, mistakes, triangles.. [Boolos] |
3357 | Democritus denies reality to large objects, because atomic entities can't combine to produce new ones [Benardete,JA on Democritus] |
598 | Democritus said that substances could never be mixed, so atoms are the substances [Democritus, by Aristotle] |
15372 | Some claim that indicative conditionals are believed by people, even though they are not actually held true [Horsten] |
1532 | Sensible qualities can't be real if they appear different to different creatures [Democritus, by Theophrastus] |
20894 | Man is separated from reality [Democritus] |
517 | All evidence comes from senses, so they are indispensable to the mind [Democritus] |
20897 | Obscure knowledge belongs to the five senses, and genuine knowledge is the other type [Democritus] |
577 | Democritus says there is either no truth, or it is concealed from us [Democritus, by Aristotle] |
20895 | We actually know nothing, and opinions are mere flux [Democritus] |
1528 | We in fact know nothing, but we each restructure our reality with beliefs [Democritus] |
492 | It is obviously impossible to understand the reality of each thing [Democritus] |
515 | We know nothing in reality; for truth lies in an abyss [Democritus] |
20892 | Democritus was devoted to discovering causal explanations [Democritus, by Eusebius] |
5882 | Democritus says soul consists of smooth round bodies brought together in accidental collision [Democritus, by Cicero] |
6034 | Atomists say soul has a rational part in the chest, and a diffused non-rational part [Democritus, by Aetius] |
20912 | The soul is the same as the mind [Democritus, by Aristotle] |
20916 | Animals have a share of reason [Democritus, by Porphyry] |
20914 | The directive centre is located in the whole head [Democritus, by Ps-Plutarch] |
6033 | Democritus said everything happens of necessity, by natural motion of atoms [Democritus, by Cicero] |
5088 | Some say there is a determinate cause for every apparently spontaneous event [Democritus, by Aristotle] |
21670 | Democritus said atoms only move by their natural motions, which are therefore necessary [Democritus, by Cicero] |
24041 | Democritus says spherical atoms are fire, and constitute the soul [psuche] [Democritus, by Aristotle] |
20913 | Democritus says the soul is the body, and thinking is thus the mixture of the body [Democritus, by Theophrastus] |
8693 | An 'abstraction principle' says two things are identical if they are 'equivalent' in some respect [Boolos] |
15347 | A theory of syntax can be based on Peano arithmetic, thanks to the translation by Gödel coding [Horsten] |
1540 | Pleasure and pain guide our choices of good and bad [Democritus] |
495 | Wisdom creates a healthy passion-free soul [Democritus] |
1537 | Happiness is identifying and separating the pleasures [Democritus, by Stobaeus] |
20917 | Contentment comes from moderation and proportion in life [Democritus, by Stobaeus] |
13551 | Democritus says wealth is a burden to the virtuous mind [Democritus, by Seneca] |
20899 | Atoms cling together, until a stronger necessity disperses them [Democritus, by Aristotle] |
20898 | Atoms are irregular, hooked, concave, convex, and many other shapes [Democritus, by Aristotle] |
20908 | There could be an atom the size of the world [Democritus, by Ps-Plutarch] |
1527 | There must be atoms, to avoid the absurdity of infinite division down to nothing [Democritus, by Aristotle] |
493 | Experiences are merely convention; only atoms and the void are real [Democritus] |
20909 | The basic atoms are without qualities - which only arise from encounters between atoms [Democritus, by Galen] |
1536 | If a cone is horizontally sliced the surfaces can't be equal, so it goes up in steps [Democritus] |
17542 | 'Full' and 'Void' secularised Parmenides's Being and Not-being [Democritus, by Heisenberg] |
1525 | Atomists say there are only three differences - in shape, arrangement and position [Democritus, by Aristotle] |
5947 | If only atoms are real and the rest is convention, we wouldn't bother to avoid pain [Democritus, by Diogenes of Oen.] |
13219 | When atoms touch, why don't they coalesce, like water drops? [Aristotle on Democritus] |
1533 | Because appearance is infinitely varied, atomists assume infinitely many shapes of atom [Democritus, by Aristotle] |
23314 | Greeks explained regularity by intellectual design, not by laws [Democritus, by Frede,M] |
24059 | Democritus is wrong: in a void we wouldn't see a distant ant in exact detail [Aristotle on Democritus] |
5101 | Movement is impossible in a void, because nothing can decide the direction of movement [Aristotle on Democritus] |
20905 | Growth and movement would not exist if there were no void to receive them [Democritus] |
20911 | There are unlimited worlds of varying sizes, some without life or water [Democritus, by Hippolytus] |
1535 | Democritus said people imagined gods as the source of what awed or frightened them [Democritus, by Sext.Empiricus] |
20915 | The soul is destroyed with the body [Democritus, by Ps-Plutarch] |