66 ideas
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] |
11211 | If a sound conclusion comes from two errors that cancel out, the path of the argument must matter [Rumfitt] |
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] |
11210 | Standardly 'and' and 'but' are held to have the same sense by having the same truth table [Rumfitt] |
11212 | The sense of a connective comes from primitively obvious rules of inference [Rumfitt] |
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] |
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] |
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] |
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] |
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] |
11214 | We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt] |
21181 | Relativity and Quantum theory give very different accounts of forces [Hesketh] |
21183 | Thermodynamics introduced work and entropy, to understand steam engine efficiency [Hesketh] |
21191 | Photons are B and W° bosons, linked by the Higgs mechanism [Hesketh] |
21199 | Spinning electric charge produces magnetism, so all fermions are magnets [Hesketh] |
21189 | Electrons may have smaller components, bound by a new force [Hesketh] |
21180 | Electrons are fundamental and are not made of anything; they are properties without size [Hesketh] |
21182 | Quantum mechanics is our only theory, and is very precise, and repeatedly confirmed [Hesketh] |
21184 | Physics was rewritten to explain stable electron orbits [Hesketh] |
21187 | Virtual particles can't be measured, and can ignore the laws of physics [Hesketh] |
21185 | Colour charge is positive or negative, and also has red, green or blue direction [Hesketh] |
21194 | The Standard Model omits gravity, because there are no particles involved [Hesketh] |
21195 | In Supersymmetry the Standard Model simplifies at high energies [Hesketh] |
21197 | Standard Model forces are one- two- and three-dimensional [Hesketh] |
21188 | Quarks and leptons have a weak charge, for the weak force [Hesketh] |
21186 | Quarks rush wildly around in protons, restrained by the gluons [Hesketh] |
21192 | Neutrinos only interact with the weak force, but decays produce them in huge numbers [Hesketh] |
21196 | To combine the forces, they must all be the same strength at some point [Hesketh] |
21190 | 'Space' in physics just means location [Hesketh] |
21193 | The universe is 68% dark energy, 27% dark matter, 5% regular matter [Hesketh] |
21198 | If a cosmic theory relies a great deal on fine-tuning basic values, it is probably wrong [Hesketh] |