144 ideas
| 5196 | Philosophy is a department of logic [Ayer] |
| 5189 | Philosophers should abandon speculation, as philosophy is wholly critical [Ayer] |
| 18835 | Logic doesn't have a metaphysical basis, but nor can logic give rise to the metaphysics [Rumfitt] |
| 7919 | Humeans rejected the a priori synthetic, and so rejected even Kantian metaphysics [Ayer, by Macdonald,C] |
| 5195 | Critics say analysis can only show the parts, and not their distinctive configuration [Ayer] |
| 5179 | Philosophy deals with the questions that scientists do not wish to handle [Ayer] |
| 5331 | You can't infer that because you have a hidden birth-mark, everybody else does [Ayer] |
| 19463 | Induction assumes some uniformity in nature, or that in some respects the future is like the past [Ayer] |
| 18819 | The idea that there are unrecognised truths is basic to our concept of truth [Rumfitt] |
| 18826 | 'True at a possibility' means necessarily true if what is said had obtained [Rumfitt] |
| 4749 | We cannot analyse the concept of 'truth', because it is simply a mark that a sentence is asserted [Ayer] |
| 18803 | Semantics for propositions: 1) validity preserves truth 2) non-contradition 3) bivalence 4) truth tables [Rumfitt] |
| 12204 | The logic of metaphysical necessity is S5 [Rumfitt] |
| 18814 | 'Absolute necessity' would have to rest on S5 [Rumfitt] |
| 18798 | It is the second-order part of intuitionistic logic which actually negates some classical theorems [Rumfitt] |
| 18799 | Intuitionists can accept Double Negation Elimination for decidable propositions [Rumfitt] |
| 18830 | Most set theorists doubt bivalence for the Continuum Hypothesis, but still use classical logic [Rumfitt] |
| 18843 | The iterated conception of set requires continual increase in axiom strength [Rumfitt] |
| 18836 | A set may well not consist of its members; the empty set, for example, is a problem [Rumfitt] |
| 18837 | A set can be determinate, because of its concept, and still have vague membership [Rumfitt] |
| 18845 | If the totality of sets is not well-defined, there must be doubt about the Power Set Axiom [Rumfitt] |
| 11211 | If a sound conclusion comes from two errors that cancel out, the path of the argument must matter [Rumfitt] |
| 18815 | Logic is higher-order laws which can expand the range of any sort of deduction [Rumfitt] |
| 9390 | Logic guides thinking, but it isn't a substitute for it [Rumfitt] |
| 18804 | The case for classical logic rests on its rules, much more than on the Principle of Bivalence [Rumfitt] |
| 18805 | Classical logic rules cannot be proved, but various lines of attack can be repelled [Rumfitt] |
| 18827 | If truth-tables specify the connectives, classical logic must rely on Bivalence [Rumfitt] |
| 12195 | Soundness in argument varies with context, and may be achieved very informally indeed [Rumfitt] |
| 12199 | There is a modal element in consequence, in assessing reasoning from suppositions [Rumfitt] |
| 12201 | We reject deductions by bad consequence, so logical consequence can't be deduction [Rumfitt] |
| 18813 | Logical consequence is a relation that can extended into further statements [Rumfitt] |
| 18808 | Normal deduction presupposes the Cut Law [Rumfitt] |
| 18840 | When faced with vague statements, Bivalence is not a compelling principle [Rumfitt] |
| 12194 | Contradictions include 'This is red and not coloured', as well as the formal 'B and not-B' [Rumfitt] |
| 11210 | Standardly 'and' and 'but' are held to have the same sense by having the same truth table [Rumfitt] |
| 18802 | In specifying a logical constant, use of that constant is quite unavoidable [Rumfitt] |
| 11212 | The sense of a connective comes from primitively obvious rules of inference [Rumfitt] |
| 12198 | Geometrical axioms in logic are nowadays replaced by inference rules (which imply the logical truths) [Rumfitt] |
| 18800 | Introduction rules give deduction conditions, and Elimination says what can be deduced [Rumfitt] |
| 18809 | Logical truths are just the assumption-free by-products of logical rules [Rumfitt] |
| 18807 | Monotonicity means there is a guarantee, rather than mere inductive support [Rumfitt] |
| 6007 | If you know your father, but don't recognise your father veiled, you know and don't know the same person [Eubulides, by Dancy,R] |
| 6006 | If you say truly that you are lying, you are lying [Eubulides, by Dancy,R] |
| 6008 | Removing one grain doesn't destroy a heap, so a heap can't be destroyed [Eubulides, by Dancy,R] |
| 18842 | Maybe an ordinal is a property of isomorphic well-ordered sets, and not itself a set [Rumfitt] |
| 17462 | A single object must not be counted twice, which needs knowledge of distinctness (negative identity) [Rumfitt] |
| 18834 | Infinitesimals do not stand in a determinate order relation to zero [Rumfitt] |
| 18846 | Cantor and Dedekind aimed to give analysis a foundation in set theory (rather than geometry) [Rumfitt] |
| 17461 | Some 'how many?' answers are not predications of a concept, like 'how many gallons?' [Rumfitt] |
| 5202 | Maths and logic are true universally because they are analytic or tautological [Ayer] |
| 6523 | Positivists regard ontology as either meaningless or stipulated [Ayer, by Robinson,H] |
| 2611 | It is currently held that quantifying over something implies belief in its existence [Ayer] |
| 9389 | Vague membership of sets is possible if the set is defined by its concept, not its members [Rumfitt] |
| 18839 | An object that is not clearly red or orange can still be red-or-orange, which sweeps up problem cases [Rumfitt] |
| 18838 | The extension of a colour is decided by a concept's place in a network of contraries [Rumfitt] |
| 16520 | We see properties necessary for a kind (in the definition), but not for an individual [Ayer] |
| 14532 | A distinctive type of necessity is found in logical consequence [Rumfitt, by Hale/Hoffmann,A] |
| 18816 | Metaphysical modalities respect the actual identities of things [Rumfitt] |
| 12193 | Logical necessity is when 'necessarily A' implies 'not-A is contradictory' [Rumfitt] |
| 12200 | A logically necessary statement need not be a priori, as it could be unknowable [Rumfitt] |
| 18825 | S5 is the logic of logical necessity [Rumfitt] |
| 12202 | Narrow non-modal logical necessity may be metaphysical, but real logical necessity is not [Rumfitt] |
| 18824 | Since possibilities are properties of the world, calling 'red' the determination of a determinable seems right [Rumfitt] |
| 18828 | If two possibilities can't share a determiner, they are incompatible [Rumfitt] |
| 12203 | If a world is a fully determinate way things could have been, can anyone consider such a thing? [Rumfitt] |
| 18821 | Possibilities are like possible worlds, but not fully determinate or complete [Rumfitt] |
| 18831 | Medieval logicians said understanding A also involved understanding not-A [Rumfitt] |
| 5183 | Only tautologies can be certain; other propositions can only be probable [Ayer] |
| 19461 | Knowing I exist reveals nothing at all about my nature [Ayer] |
| 19459 | To say 'I am not thinking' must be false, but it might have been true, so it isn't self-contradictory [Ayer] |
| 19460 | 'I know I exist' has no counterevidence, so it may be meaningless [Ayer] |
| 6525 | Logical positivists could never give the sense-data equivalent of 'there is a table next door' [Robinson,H on Ayer] |
| 5170 | Material things are constructions from actual and possible occurrences of sense-contents [Ayer] |
| 8824 | No one has defended translational phenomenalism since Ayer in 1940 [Ayer, by Kim] |
| 2614 | Modern phenomenalism holds that objects are logical constructions out of sense-data [Ayer] |
| 5198 | We could verify 'a thing can't be in two places at once' by destroying one of the things [Ierubino on Ayer] |
| 2619 | Whether geometry can be applied to reality is an empirical question outside of geometry [Ayer] |
| 5197 | By changing definitions we could make 'a thing can't be in two places at once' a contradiction [Ayer] |
| 5204 | To say that a proposition is true a priori is to say that it is a tautology [Ayer] |
| 2615 | The concept of sense-data allows us to discuss appearances without worrying about reality [Ayer] |
| 6524 | Positivists prefer sense-data to objects, because the vocabulary covers both illusions and perceptions [Ayer, by Robinson,H] |
| 5193 | Causal and representative theories of perception are wrong as they refer to unobservables [Ayer] |
| 5200 | The main claim of rationalism is that thought is an independent source of knowledge [Ayer] |
| 4729 | Empiricism lacked a decent account of the a priori, until Ayer said it was entirely analytic [O'Grady on Ayer] |
| 5180 | All propositions (especially 'metaphysics') must begin with the senses [Ayer] |
| 5169 | My empiricism logically distinguishes analytic and synthetic propositions, and metaphysical verbiage [Ayer] |
| 5185 | It is further sense-experience which informs us of the mistakes that arise out of sense-experience [Ayer] |
| 5199 | Empiricism, it is said, cannot account for our knowledge of necessary truths [Ayer] |
| 18820 | In English 'evidence' is a mass term, qualified by 'little' and 'more' [Rumfitt] |
| 5163 | Basic propositions refer to a single experience, are incorrigible, and conclusively verifiable [Ayer] |
| 19464 | We only discard a hypothesis after one failure if it appears likely to keep on failing [Ayer] |
| 5190 | The induction problem is to prove generalisations about the future based on the past [Ayer] |
| 19462 | Induction passes from particular facts to other particulars, or to general laws, non-deductively [Ayer] |
| 5191 | We can't use the uniformity of nature to prove induction, as that would be circular [Ayer] |
| 5177 | Other minds are 'metaphysical' objects, because I can never observe their experiences [Ayer] |
| 5662 | Maybe induction could never prove the existence of something unobservable [Ayer] |
| 5178 | A conscious object is by definition one that behaves in a certain way, so behaviour proves consciousness [Ayer] |
| 5167 | The argument from analogy fails, so the best account of other minds is behaviouristic [Ayer] |
| 2613 | The theory of other minds has no rival [Ayer] |
| 5328 | Originally I combined a mentalistic view of introspection with a behaviouristic view of other minds [Ayer] |
| 5330 | Physicalism undercuts the other mind problem, by equating experience with 'public' brain events [Ayer] |
| 5664 | Consciousness must involve a subject, and only bodies identify subjects [Ayer] |
| 5172 | If the self is meaningful, it must be constructed from sense-experiences [Ayer] |
| 5326 | Qualia must be united by a subject, because they lead to concepts and judgements [Ayer] |
| 5325 | Is something an 'experience' because it relates to other experiences, or because it relates to a subject? [Ayer] |
| 5324 | Bodily identity and memory work together to establish personal identity [Ayer] |
| 5173 | Two experiences belong to one self if their contents belong with one body [Ayer] |
| 5176 | Empiricists can define personal identity as bodily identity, which consists of sense-contents [Ayer] |
| 5668 | People own conscious states because they are causally related to the identifying body [Ayer] |
| 5322 | Self-consciousness is not basic, because experiences are not instrinsically marked with ownership [Ayer] |
| 5661 | We identify experiences by their owners, so we can't define owners by their experiences [Ayer] |
| 5665 | Memory is the best proposal as what unites bundles of experiences [Ayer] |
| 5666 | Not all exerience can be remembered, as this would produce an infinite regress [Ayer] |
| 5327 | Temporal gaps in the consciousness of a spirit could not be bridged by memories [Ayer] |
| 5669 | Personal identity can't just be relations of experiences, because the body is needed to identify them [Ayer] |
| 5171 | The supposed 'gulf' between mind and matter is based on the senseless concept of 'substances' [Ayer] |
| 5329 | Why shouldn't we say brain depends on mind? Better explanation! [Ayer] |
| 18817 | We understand conditionals, but disagree over their truth-conditions [Rumfitt] |
| 5181 | A sentence is factually significant to someone if they know how to verify its proposition [Ayer] |
| 5184 | Factual propositions imply (in conjunction with a few other premises) possible experiences [Ayer] |
| 5186 | Tautologies and empirical hypotheses form the entire class of significant propositions [Ayer] |
| 5164 | A statement is meaningful if observation statements can be deduced from it [Ayer] |
| 5165 | Directly verifiable statements must entail at least one new observation statement [Ayer] |
| 5166 | The principle of verification is not an empirical hypothesis, but a definition [Ayer] |
| 5162 | Sentences only express propositions if they are meaningful; otherwise they are 'statements' [Ayer] |
| 2610 | Talk of propositions is just shorthand for talking about equivalent sentences [Ayer] |
| 18829 | The truth grounds for 'not A' are the possibilities incompatible with truth grounds for A [Rumfitt] |
| 11214 | We learn 'not' along with affirmation, by learning to either affirm or deny a sentence [Rumfitt] |
| 6968 | Some people think there are ethical facts, but of a 'queer' sort [Ayer] |
| 6972 | A right attitude is just an attitude one is prepared to stand by [Ayer] |
| 6973 | Moral theories are all meta-ethical, and are neutral as regards actual conduct [Ayer] |
| 6974 | Moral judgements cannot be the logical consequence of a moral philosophy [Ayer] |
| 5205 | Moral intuition is worthless if there is no criterion to decide between intuitions [Ayer] |
| 6971 | I would describe intuitions of good as feelings of approval [Ayer] |
| 23725 | Ayer defends the emotivist version of expressivism [Ayer, by Smith,M] |
| 5206 | To say an act is wrong makes no further statement about it, but merely expresses disapproval [Ayer] |
| 6969 | Approval of historical or fictional murders gives us leave to imitate them [Ayer] |
| 6970 | Moral judgements are not expressions, but are elements in a behaviour pattern [Ayer] |
| 5168 | Moral approval and disapproval concerns classes of actions, rather than particular actions [Ayer] |
| 15251 | The attribution of necessity to causation is either primitive animism, or confusion with logical necessity [Ayer] |
| 5208 | A person with non-empirical attributes is unintelligible. [Ayer] |
| 5187 | When we ascribe an attribute to a thing, we covertly assert that it exists [Ayer] |
| 5207 | If theism is non-sensical, then so is atheism. [Ayer] |
| 5209 | The 'truths' expressed by theists are not literally significant [Ayer] |