64 ideas
21584 | A sense of timelessness is essential to wisdom [Russell] |
21757 | Philosophy is the conceptual essence of the shape of history [Hegel] |
21572 | Philosophical disputes are mostly hopeless, because philosophers don't understand each other [Russell] |
21571 | Philosophical systems are interesting, but we now need a more objective scientific philosophy [Russell] |
21574 | Hegel's confusions over 'is' show how vast systems can be built on simple errors [Russell] |
21587 | Philosophers sometimes neglect truth and distort facts to attain a nice system [Russell] |
21582 | Physicists accept particles, points and instants, while pretending they don't do metaphysics [Russell] |
21573 | When problems are analysed properly, they are either logical, or not philosophical at all [Russell] |
10987 | Three traditional names of rules are 'Simplification', 'Addition' and 'Disjunctive Syllogism' [Read] |
11004 | Necessity is provability in S4, and true in all worlds in S5 [Read] |
11018 | There are fuzzy predicates (and sets), and fuzzy quantifiers and modifiers [Read] |
11011 | Same say there are positive, negative and neuter free logics [Read] |
11020 | Realisms like the full Comprehension Principle, that all good concepts determine sets [Read] |
21588 | Logic gives the method of research in philosophy [Russell] |
10986 | Not all validity is captured in first-order logic [Read] |
10972 | The non-emptiness of the domain is characteristic of classical logic [Read] |
11024 | Semantics must precede proof in higher-order logics, since they are incomplete [Read] |
10985 | We should exclude second-order logic, precisely because it captures arithmetic [Read] |
10970 | A theory of logical consequence is a conceptual analysis, and a set of validity techniques [Read] |
10984 | Logical consequence isn't just a matter of form; it depends on connections like round-square [Read] |
21586 | The logical connectives are not objects, but are formal, and need a context [Russell] |
10973 | A theory is logically closed, which means infinite premisses [Read] |
11007 | Quantifiers are second-order predicates [Read] |
10978 | In second-order logic the higher-order variables range over all the properties of the objects [Read] |
10971 | A logical truth is the conclusion of a valid inference with no premisses [Read] |
10988 | Any first-order theory of sets is inadequate [Read] |
10974 | Compactness is when any consequence of infinite propositions is the consequence of a finite subset [Read] |
10975 | Compactness does not deny that an inference can have infinitely many premisses [Read] |
10977 | Compactness blocks the proof of 'for every n, A(n)' (as the proof would be infinite) [Read] |
10976 | Compactness makes consequence manageable, but restricts expressive power [Read] |
21585 | The tortoise won't win, because infinite instants don't compose an infinitely long time [Russell] |
11014 | Self-reference paradoxes seem to arise only when falsity is involved [Read] |
11025 | Infinite cuts and successors seems to suggest an actual infinity there waiting for us [Read] |
10979 | Although second-order arithmetic is incomplete, it can fully model normal arithmetic [Read] |
10980 | Second-order arithmetic covers all properties, ensuring categoricity [Read] |
10997 | Von Neumann numbers are helpful, but don't correctly describe numbers [Read] |
21684 | Atomic facts may be inferrable from others, but never from non-atomic facts [Russell] |
22316 | A positive and negative fact have the same constituents; their difference is primitive [Russell] |
11016 | Would a language without vagueness be usable at all? [Read] |
11019 | Supervaluations say there is a cut-off somewhere, but at no particular place [Read] |
11012 | A 'supervaluation' gives a proposition consistent truth-value for classical assignments [Read] |
11013 | Identities and the Indiscernibility of Identicals don't work with supervaluations [Read] |
21576 | With asymmetrical relations (before/after) the reduction to properties is impossible [Russell] |
21575 | When we attribute a common quality to a group, we can forget the quality and just talk of the group [Russell] |
10995 | A haecceity is a set of individual properties, essential to each thing [Read] |
11001 | Equating necessity with truth in every possible world is the S5 conception of necessity [Read] |
10992 | The point of conditionals is to show that one will accept modus ponens [Read] |
10989 | The standard view of conditionals is that they are truth-functional [Read] |
11017 | Some people even claim that conditionals do not express propositions [Read] |
10983 | Knowledge of possible worlds is not causal, but is an ontology entailed by semantics [Read] |
10982 | How can modal Platonists know the truth of a modal proposition? [Read] |
10996 | Actualism is reductionist (to parts of actuality), or moderate realist (accepting real abstractions) [Read] |
10981 | A possible world is a determination of the truth-values of all propositions of a domain [Read] |
11000 | If worlds are concrete, objects can't be present in more than one, and can only have counterparts [Read] |
21580 | Science condemns sense-data and accepts matter, but a logical construction must link them [Russell] |
21583 | When sense-data change, there must be indistinguishable sense-data in the process [Russell] |
21577 | Empirical truths are particular, so general truths need an a priori input of generality [Russell] |
21579 | Objects are treated as real when they connect with other experiences in a normal way [Russell] |
21578 | Global scepticism is irrefutable, but can't replace our other beliefs, and just makes us hesitate [Russell] |
6416 | Other minds seem to exist, because their testimony supports realism about the world [Russell, by Grayling] |
10998 | The mind abstracts ways things might be, which are nonetheless real [Read] |
11005 | Negative existentials with compositionality make the whole sentence meaningless [Read] |
10966 | A proposition objectifies what a sentence says, as indicative, with secure references [Read] |
21581 | We never experience times, but only succession of events [Russell] |