118 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] |
13515 | To study abstract problems, some knowledge of set theory is essential [Hart,WD] |
11283 | There is pure deductive reasoning, and explanatory demonstration reasoning [Aristotle, by Politis] |
1672 | Maybe everything could be demonstrated, if demonstration can be reciprocal or circular [Aristotle] |
1684 | Two falsehoods can be contrary to one another [Aristotle] |
12145 | Definitions are of what something is, and that is universal [Aristotle] |
12075 | An Aristotelian definition is causal [Aristotle, by Witt] |
12384 | Definition by division needs predicates, which are well ordered and thorough [Aristotle] |
9066 | You can define objects by progressively identifying what is the same and what is different [Aristotle] |
12382 | What it is and why it is are the same; screening defines and explains an eclipse [Aristotle] |
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] |
1668 | An axiom is a principle which must be understood if one is to learn anything [Aristotle] |
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] |
13481 | Maybe sets should be rethought in terms of the even more basic categories [Hart,WD] |
12376 | Demonstrations by reductio assume excluded middle [Aristotle] |
12373 | Something holds universally when it is proved of an arbitrary and primitive case [Aristotle] |
12363 | Everything is either asserted or denied truly [Aristotle] |
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] |
13004 | Aristotle's axioms (unlike Euclid's) are assumptions awaiting proof [Aristotle, by Leibniz] |
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] |
12377 | Mathematics is concerned with forms, not with superficial properties [Aristotle] |
12372 | The essence of a triangle comes from the line, mentioned in any account of triangles [Aristotle] |
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] |
12369 | A unit is what is quantitatively indivisible [Aristotle] |
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] |
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] |
18910 | To seek truth, study the real connections between subjects and attributes [Aristotle] |
1675 | Separate Forms aren't needed for logic, but universals (one holding of many) are essential [Aristotle] |
1677 | We can forget the Forms, as they are irrelevant, and not needed in giving demonstrations [Aristotle] |
1687 | Why are being terrestrial and a biped combined in the definition of man, but being literate and musical aren't? [Aristotle] |
1681 | Units are positionless substances, and points are substances with position [Aristotle] |
14381 | A statue is essentially the statue, but its lump is not essentially a statue, so statue isn't lump [Yablo, by Rocca] |
12146 | Definitions recognise essences, so are not themselves essences [Aristotle] |
17039 | The predicates of a thing's nature are necessary to it [Aristotle] |
11994 | Aristotelian essences are properties mentioned at the starting point of a science [Aristotle, by Kung] |
12381 | What is necessary cannot be otherwise [Aristotle] |
1690 | A stone travels upwards by a forced necessity, and downwards by natural necessity [Aristotle] |
12072 | For Aristotle knowledge is explanatory, involving understanding, and principles or causes [Aristotle, by Witt] |
12073 | 'Episteme' means grasping causes, universal judgments, explanation, and teaching [Aristotle, by Witt] |
12378 | The reason why is the key to knowledge [Aristotle] |
12364 | We understand a thing when we know its explanation and its necessity [Aristotle] |
12366 | We only understand something when we know its explanation [Aristotle] |
12370 | Some understanding, of immediate items, is indemonstrable [Aristotle] |
1685 | No one has mere belief about something if they think it HAS to be true [Aristotle] |
1673 | Knowledge proceeds from principles, so it is hard to know if we know [Aristotle] |
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] |
12379 | You cannot understand anything through perception [Aristotle] |
16725 | Some knowledge is lost if you lose a sense, and there is no way the knowledge can be replaced [Aristotle] |
23309 | Aristotle's concepts of understanding and explanation mean he is not a pure empiricist [Aristotle, by Frede,M] |
1693 | Animals may have some knowledge if they retain perception, but understanding requires reasons to be given [Aristotle] |
9067 | Many memories of the same item form a single experience [Aristotle] |
1671 | Sceptics say justification is an infinite regress, or it stops at the unknowable [Aristotle] |
1670 | When you understand basics, you can't be persuaded to change your mind [Aristotle] |
1691 | Aim to get definitions of the primitive components, thus establishing the kind, and work towards the attributes [Aristotle] |
12383 | There must be definitions before demonstration is possible [Aristotle] |
1674 | All demonstration is concerned with existence, axioms and properties [Aristotle] |
24068 | Demonstration is more than entailment, as the explanatory order must match the causal order [Aristotle, by Koslicki] |
17310 | Aristotle gets asymmetric consequence from demonstration, which reflects real causal priority [Aristotle, by Koslicki] |
21359 | Aristotle doesn't actually apply his theory of demonstration to his practical science [Leroi on Aristotle] |
1667 | Premises must be true, primitive and immediate, and prior to and explanatory of conclusions [Aristotle] |
12365 | We can know by demonstration, which is a scientific deduction leading to understanding [Aristotle] |
10918 | Demonstrative understanding rests on necessary features of the thing in itself [Aristotle] |
12374 | Demonstrations must be necessary, and that depends on the middle term [Aristotle] |
12148 | Demonstrations are syllogisms which give explanations [Aristotle] |
1679 | Universal demonstrations are about thought; particular demonstrations lead to perceptions [Aristotle] |
1680 | Demonstration is better with fewer presuppositions, and it is quicker if these are familiar [Aristotle] |
12147 | The principles of demonstrations are definitions [Aristotle] |
12371 | A demonstration is a deduction which proceeds from necessities [Aristotle] |
1683 | We learn universals from many particulars [Aristotle] |
12367 | What is most universal is furthest away, and the particulars are nearest [Aristotle] |
12385 | Are particulars explained more by universals, or by other particulars? [Aristotle] |
12380 | Universals are valuable because they make the explanations plain [Aristotle] |
1689 | Explanation is of the status of a thing, inferences to it, initiation of change, and purpose [Aristotle] |
1686 | What we seek and understand are facts, reasons, existence, and identity [Aristotle] |
12357 | Explanation and generality are inseparable [Aristotle, by Wedin] |
1669 | The foundation or source is stronger than the thing it causes [Aristotle] |
1678 | Universals give better explanations, because they are self-explanatory and primitive [Aristotle] |
9068 | Perception creates primitive immediate principles by building a series of firm concepts [Aristotle] |
9069 | A perception lodging in the soul creates a primitive universal, which becomes generalised [Aristotle] |
13475 | The Fregean concept of GREEN is a function assigning true to green things, and false to the rest [Hart,WD] |
9070 | We learn primitives and universals by induction from perceptions [Aristotle] |
12368 | Negation takes something away from something [Aristotle] |
1692 | If you shouldn't argue in metaphors, then you shouldn't try to define them either [Aristotle] |
12375 | Whatever holds of a kind intrinsically holds of it necessarily [Aristotle] |
1688 | Properties must be proved, but not essence; but existents are not a kind, so existence isn't part of essence [Aristotle] |