73 ideas
13466 | We are all post-Kantians, because he set the current agenda for philosophy [Hart,WD] |
13477 | The problems are the monuments of philosophy [Hart,WD] |
6420 | Only by analysing is progress possible in philosophy [Russell] |
6432 | Analysis gives new knowledge, without destroying what we already have [Russell] |
13515 | To study abstract problems, some knowledge of set theory is essential [Hart,WD] |
6437 | The theory of types makes 'Socrates and killing are two' illegitimate [Russell] |
6442 | Truth belongs to beliefs, not to propositions and sentences [Russell] |
13469 | Tarski showed how we could have a correspondence theory of truth, without using 'facts' [Hart,WD] |
13504 | Truth for sentences is satisfaction of formulae; for sentences, either all sequences satisfy it (true) or none do [Hart,WD] |
13503 | A first-order language has an infinity of T-sentences, which cannot add up to a definition of truth [Hart,WD] |
13500 | Conditional Proof: infer a conditional, if the consequent can be deduced from the antecedent [Hart,WD] |
13502 | ∃y... is read as 'There exists an individual, call it y, such that...', and not 'There exists a y such that...' [Hart,WD] |
13456 | Set theory articulates the concept of order (through relations) [Hart,WD] |
13497 | Nowadays ZFC and NBG are the set theories; types are dead, and NF is only useful for the whole universe [Hart,WD] |
13443 | ∈ relates across layers, while ⊆ relates within layers [Hart,WD] |
13442 | Without the empty set we could not form a∩b without checking that a and b meet [Hart,WD] |
13493 | In the modern view, foundation is the heart of the way to do set theory [Hart,WD] |
13495 | Foundation Axiom: an nonempty set has a member disjoint from it [Hart,WD] |
13461 | We can choose from finite and evident sets, but not from infinite opaque ones [Hart,WD] |
13462 | With the Axiom of Choice every set can be well-ordered [Hart,WD] |
13516 | If we accept that V=L, it seems to settle all the open questions of set theory [Hart,WD] |
13441 | Naïve set theory has trouble with comprehension, the claim that every predicate has an extension [Hart,WD] |
13494 | The iterative conception may not be necessary, and may have fixed points or infinitely descending chains [Hart,WD] |
13457 | A 'partial ordering' is irreflexive and transitive; the sets are ordered, but not the subsets [Hart,WD] |
13458 | A partial ordering becomes 'total' if any two members of its field are comparable [Hart,WD] |
13460 | 'Well-ordering' must have a least member, so it does the natural numbers but not the integers [Hart,WD] |
13490 | Von Neumann defines α<β as α∈β [Hart,WD] |
6436 | I gradually replaced classes with properties, and they ended as a symbolic convenience [Russell] |
13481 | Maybe sets should be rethought in terms of the even more basic categories [Hart,WD] |
7528 | Leibniz bases everything on subject/predicate and substance/property propositions [Russell] |
6439 | Names are meaningless unless there is an object which they designate [Russell] |
13506 | The universal quantifier can't really mean 'all', because there is no universal set [Hart,WD] |
13512 | Modern model theory begins with the proof of Los's Conjecture in 1962 [Hart,WD] |
13505 | Model theory studies how set theory can model sets of sentences [Hart,WD] |
13511 | Model theory is mostly confined to first-order theories [Hart,WD] |
13513 | Models are ways the world might be from a first-order point of view [Hart,WD] |
13496 | First-order logic is 'compact': consequences of a set are consequences of a finite subset [Hart,WD] |
13484 | Berry's Paradox: we succeed in referring to a number, with a term which says we can't do that [Hart,WD] |
13482 | The Burali-Forti paradox is a crisis for Cantor's ordinals [Hart,WD] |
13507 | The machinery used to solve the Liar can be rejigged to produce a new Liar [Hart,WD] |
13459 | The less-than relation < well-orders, and partially orders, and totally orders the ordinal numbers [Hart,WD] |
13491 | The axiom of infinity with separation gives a least limit ordinal ω [Hart,WD] |
13463 | There are at least as many infinite cardinals as transfinite ordinals (because they will map) [Hart,WD] |
13492 | Von Neumann's ordinals generalise into the transfinite better, because Zermelo's ω is a singleton [Hart,WD] |
13446 | 19th century arithmetization of analysis isolated the real numbers from geometry [Hart,WD] |
13509 | We can establish truths about infinite numbers by means of induction [Hart,WD] |
13474 | Euclid has a unique parallel, spherical geometry has none, and saddle geometry has several [Hart,WD] |
6423 | We tried to define all of pure maths using logical premisses and concepts [Russell] |
13471 | Mathematics makes existence claims, but philosophers usually say those are never analytic [Hart,WD] |
6424 | Formalists say maths is merely conventional marks on paper, like the arbitrary rules of chess [Russell] |
6425 | Formalism can't apply numbers to reality, so it is an evasion [Russell] |
6426 | Intuitionism says propositions are only true or false if there is a method of showing it [Russell] |
6419 | In 1899-1900 I adopted the philosophy of logical atomism [Russell] |
6438 | Complex things can be known, but not simple things [Russell] |
13488 | Mass words do not have plurals, or numerical adjectives, or use 'fewer' [Hart,WD] |
6434 | Facts are everything, except simples; they are either relations or qualities [Russell] |
6440 | Universals can't just be words, because words themselves are universals [Russell] |
6430 | In epistemology we should emphasis the continuity between animal and human minds [Russell] |
13480 | Fregean self-evidence is an intrinsic property of basic truths, rules and definitions [Hart,WD] |
13476 | The failure of key assumptions in geometry, mereology and set theory throw doubt on the a priori [Hart,WD] |
6441 | Pragmatism judges by effects, but I judge truth by causes [Russell] |
6431 | Empiricists seem unclear what they mean by 'experience' [Russell] |
6444 | True belief about the time is not knowledge if I luckily observe a stopped clock at the right moment [Russell] |
6433 | Behaviourists struggle to explain memory and imagination, because they won't admit images [Russell] |
6443 | Surprise is a criterion of error [Russell] |
13475 | The Fregean concept of GREEN is a function assigning true to green things, and false to the rest [Hart,WD] |
6427 | Unverifiable propositions about the remote past are still either true or false [Russell] |
6435 | You can believe the meaning of a sentence without thinking of the words [Russell] |
12163 | Literary meaning emerges in comparisons, and tradition shows which comparisons are relevant [Scruton] |
12162 | In literature, word replacement changes literary meaning [Scruton] |
12159 | Without intentions we can't perceive sculpture, but that is not the whole story [Scruton] |
12160 | In aesthetic interest, even what is true is treated as though it were not [Scruton] |
12161 | We can be objective about conventions, but love of art is needed to understand its traditions [Scruton] |