61 ideas
291 | Don't assume that wisdom is the automatic consequence of old age [Plato] |
13520 | A 'tautology' must include connectives [Wolf,RS] |
13524 | Deduction Theorem: T∪{P}|-Q, then T|-(P→Q), which justifies Conditional Proof [Wolf,RS] |
13522 | Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [Wolf,RS] |
13521 | Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance [Wolf,RS] |
13523 | Existential Generalization (or 'proof by example'): if we can say P(t), then we can say something is P [Wolf,RS] |
13529 | Empty Set: ∃x∀y ¬(y∈x). The unique empty set exists [Wolf,RS] |
13526 | Comprehension Axiom: if a collection is clearly specified, it is a set [Wolf,RS] |
13534 | In first-order logic syntactic and semantic consequence (|- and |=) nicely coincide [Wolf,RS] |
13535 | First-order logic is weakly complete (valid sentences are provable); we can't prove every sentence or its negation [Wolf,RS] |
13531 | Model theory reveals the structures of mathematics [Wolf,RS] |
13532 | Model theory 'structures' have a 'universe', some 'relations', some 'functions', and some 'constants' [Wolf,RS] |
13519 | Model theory uses sets to show that mathematical deduction fits mathematical truth [Wolf,RS] |
13533 | First-order model theory rests on completeness, compactness, and the Löwenheim-Skolem-Tarski theorem [Wolf,RS] |
13537 | An 'isomorphism' is a bijection that preserves all structural components [Wolf,RS] |
13539 | The LST Theorem is a serious limitation of first-order logic [Wolf,RS] |
13538 | If a theory is complete, only a more powerful language can strengthen it [Wolf,RS] |
13525 | Most deductive logic (unlike ordinary reasoning) is 'monotonic' - we don't retract after new givens [Wolf,RS] |
13530 | An ordinal is an equivalence class of well-orderings, or a transitive set whose members are transitive [Wolf,RS] |
13518 | Modern mathematics has unified all of its objects within set theory [Wolf,RS] |
5937 | The goodness of opinions depends on their grounds, and corresponding degrees of conviction [Ross] |
5936 | Knowledge is superior to opinion because it is certain [Ross] |
5927 | I prefer the causal theory to sense data, because sensations are events, not apprehensions [Ross] |
5940 | Two goods may be comparable, although they are not commensurable [Ross] |
5924 | Identical objects must have identical value [Ross] |
5933 | Aesthetic enjoyment combines pleasure with insight [Ross] |
5928 | Beauty is neither objective nor subjective, but a power of producing certain mental events [Ross] |
5911 | Moral duties are as fundamental to the universe as the axioms of mathematics [Ross] |
5926 | The beauty of a patch of colour might be the most important fact about it [Ross] |
7259 | Ross said moral principles are self-evident from the facts, but not from pure thought [Ross, by Dancy,J] |
5913 | The moral convictions of thoughtful educated people are the raw data of ethics [Ross] |
5920 | Value is held to be either a quality, or a relation (usually between a thing and a mind) [Ross] |
5923 | The arguments for value being an objective or a relation fail, so it appears to be a quality [Ross] |
5918 | The thing is intrinsically good if it would be good when nothing else existed [Ross] |
5930 | All things being equal, we all prefer the virtuous to be happy, not the vicious [Ross] |
5922 | An instrumentally good thing might stay the same, but change its value because of circumstances [Ross] |
5921 | We can ask of pleasure or beauty whether they are valuable, but not of goodness [Ross] |
5932 | The four goods are: virtue, pleasure, just allocation of pleasure, and knowledge [Ross] |
5910 | The three intrinsic goods are virtue, knowledge and pleasure [Ross] |
5898 | 'Right' and 'good' differ in meaning, as in a 'right action' and a 'good man' [Ross] |
5899 | If there are two equally good acts, they may both be right, but neither a duty [Ross] |
5904 | In the past 'right' just meant what is conventionally accepted [Ross] |
5919 | Goodness is a wider concept than just correct ethical conduct [Ross] |
5941 | Motives decide whether an action is good, and what is done decides whether it was right [Ross] |
5938 | Virtue is superior to pleasure, as pleasure is never a duty, but goodness is [Ross] |
5931 | All other things being equal, a universe with more understanding is better [Ross] |
5939 | Morality is not entirely social; a good moral character should love truth [Ross] |
5905 | We clearly value good character or understanding, as well as pleasure [Ross] |
5929 | No one thinks it doesn't matter whether pleasure is virtuously or viciously acquired [Ross] |
5906 | Promise-keeping is bound by the past, and is not concerned with consequences [Ross] |
18622 | Promises create a new duty to a particular person; they aren't just a strategy to achieve well-being [Ross] |
5908 | Prima facie duties rest self-evidently on particular circumstance [Ross] |
293 | Being unafraid (perhaps through ignorance) and being brave are two different things [Plato] |
5917 | People lose their rights if they do not respect the rights of others [Ross] |
5900 | We should do our duty, but not from a sense of duty [Ross] |
5942 | We like people who act from love, but admire more the people who act from duty [Ross] |
5909 | Be faithful, grateful, just, beneficent, non-malevolent, and improve yourself [Ross, by PG] |
5914 | An act may be described in innumerable ways [Ross] |
5912 | We should use money to pay debts before giving to charity [Ross] |
5916 | Rights were originally legal, and broadened to include other things [Ross] |
5915 | Rights can be justly claimed, so animals have no rights, as they cannot claim any [Ross] |