73 ideas
13466 | We are all post-Kantians, because he set the current agenda for philosophy [Hart,WD] |
3600 | Slow and accurate thought makes the greatest progress [Descartes] |
13477 | The problems are the monuments of philosophy [Hart,WD] |
3601 | Most things in human life seem vain and useless [Descartes] |
3602 | Almost every daft idea has been expressed by some philosopher [Descartes] |
13515 | To study abstract problems, some knowledge of set theory is essential [Hart,WD] |
3603 | Methodical thinking is cautious, analytical, systematic, and panoramic [Descartes, by PG] |
3612 | Clear and distinct conceptions are true because a perfect God exists [Descartes] |
3610 | Truth is clear and distinct conception - of which it is hard to be sure [Descartes] |
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] |
17884 | Mathematical set theory has many plausible stopping points, such as finitism, and predicativism [Koellner] |
17893 | 'Reflection principles' say the whole truth about sets can't be captured [Koellner] |
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] |
13490 | Von Neumann defines α<β as α∈β [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] |
13481 | Maybe sets should be rethought in terms of the even more basic categories [Hart,WD] |
13506 | The universal quantifier can't really mean 'all', because there is no universal set [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] |
13512 | Modern model theory begins with the proof of Los's Conjecture in 1962 [Hart,WD] |
17894 | We have no argument to show a statement is absolutely undecidable [Koellner] |
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] |
13492 | Von Neumann's ordinals generalise into the transfinite better, because Zermelo's ω is a singleton [Hart,WD] |
13459 | The less-than relation < well-orders, and partially orders, and totally orders the ordinal numbers [Hart,WD] |
13463 | There are at least as many infinite cardinals as transfinite ordinals (because they will map) [Hart,WD] |
13491 | The axiom of infinity with separation gives a least limit ordinal ω [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] |
17890 | There are at least eleven types of large cardinal, of increasing logical strength [Koellner] |
13474 | Euclid has a unique parallel, spherical geometry has none, and saddle geometry has several [Hart,WD] |
17887 | PA is consistent as far as we can accept, and we expand axioms to overcome limitations [Koellner] |
17891 | Arithmetical undecidability is always settled at the next stage up [Koellner] |
13471 | Mathematics makes existence claims, but philosophers usually say those are never analytic [Hart,WD] |
13488 | Mass words do not have plurals, or numerical adjectives, or use 'fewer' [Hart,WD] |
3605 | We can believe a thing without knowing we believe it [Descartes] |
1583 | In morals Descartes accepts the conventional, but rejects it in epistemology [Roochnik on Descartes] |
3607 | In thinking everything else false, my own existence remains totally certain [Descartes] |
13480 | Fregean self-evidence is an intrinsic property of basic truths, rules and definitions [Hart,WD] |
3617 | I aim to find the principles and causes of everything, using the seeds within my mind [Descartes] |
13476 | The failure of key assumptions in geometry, mereology and set theory throw doubt on the a priori [Hart,WD] |
3611 | Understanding, rather than imagination or senses, gives knowledge [Descartes] |
3606 | I was searching for reliable rock under the shifting sand [Descartes] |
3604 | When rebuilding a house, one needs alternative lodgings [Descartes] |
3618 | Only experiments can settle disagreements between rival explanations [Descartes] |
3615 | Little reason is needed to speak, so animals have no reason at all [Descartes] |
3609 | I am a thinking substance, which doesn't need a place or material support [Descartes] |
3608 | I can deny my body and the world, but not my own existence [Descartes] |
3613 | Reason is universal in its responses, but a physical machine is constrained by its organs [Descartes] |
3616 | The soul must unite with the body to have appetites and sensations [Descartes] |
3614 | A machine could speak in response to physical stimulus, but not hold a conversation [Descartes] |
13475 | The Fregean concept of GREEN is a function assigning true to green things, and false to the rest [Hart,WD] |
1581 | Greeks elevate virtues enormously, but never explain them [Descartes] |
16686 | God has established laws throughout nature, and implanted ideas of them within us [Descartes] |