90 ideas
| 3358 | Metaphysics focuses on Platonism, essentialism, materialism and anti-realism [Benardete,JA] |
| Full Idea: In contemporary metaphysics the major areas of discussion are Platonism, essentialism, materialism and anti-realism. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], After) |
| 3312 | There are the 'is' of predication (a function), the 'is' of identity (equals), and the 'is' of existence (quantifier) [Benardete,JA] |
| Full Idea: At least since Russell, one has routinely distinguished between the 'is' of predication ('Socrates is wise', Fx), the 'is' of identity ('Morning Star is Evening Star', =), and the 'is' of existence ('the cat is under the bed', Ex). | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 7) | |
| A reaction: This seems horribly nitpicking to many people, but I love it - because it is just true, and it is a truth right at the basis of the confusions in our talk. Analytic philosophy forever! [P.S. 'Tiddles is a cat' - the 'is' membership] |
| 3352 | Analytical philosophy analyses separate concepts successfully, but lacks a synoptic vision of the results [Benardete,JA] |
| Full Idea: Analytical philosophy excels in the piecemeal analysis of causation, perception, knowledge and so on, but there is a striking poverty of any synoptic vision of these independent studies. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.22) |
| 9136 | The paradox of analysis says that any conceptual analysis must be either trivial or false [Sorensen] |
| Full Idea: The paradox of analysis says if a conceptual analysis states exactly what the original statement says, then the analysis is trivial; if it says something different from the original, then the analysis is mistaken. All analyses are trivial or false. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 8.5) | |
| A reaction: [source is G.E. Moore] Good analyses typically give explanations, or necessary and sufficient conditions, or inferential relations. At their most trivial they at least produce a more profound dictionary than your usual lexicographer. Not guilty. |
| 3329 | Presumably the statements of science are true, but should they be taken literally or not? [Benardete,JA] |
| Full Idea: As our bible, the Book of Science is presumed to contain only true sentences, but it is less clear how they are to be construed, which literally and which non-literally. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.13) |
| 9131 | Two long understandable sentences can have an unintelligible conjunction [Sorensen] |
| Full Idea: If there is an upper bound on the length of understandable sentences, then two understandable sentences can have an unintelligible conjunction. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 6.4) | |
| A reaction: Not a huge paradox about the use of the word 'and', perhaps, but a nice little warning to be clear about what is being claimed before you cheerfully assert a screamingly obvious law of thought, such as conjunction. |
| 9139 | If nothing exists, no truthmakers could make 'Nothing exists' true [Sorensen] |
| Full Idea: If nothing exists, then there are no truthmakers that could make 'Nothing exists' true. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 11.2) | |
| A reaction: [He cites David Lewis] We may be confusing truth with facts. I take facts to be independent of minds, but truth only makes sense as a concept in the presence of minds which are endeavouring to think well. |
| 9140 | Which toothbrush is the truthmaker for 'buy one, get one free'? [Sorensen] |
| Full Idea: If I buy two toothbrushes on a 'buy one, get one free' offer, which one did I buy and which one did I get free? Those who believe that each contingent truth has a truthmaker are forced to believe that 'buy one, get one free' is false. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 11.6) | |
| A reaction: Nice. There really is no fact of which toothbrush is the free one. The underlying proposition must presumably be 'two for the price of one'. But you could hardly fault the first slogan under the Trades Descriptions Act. |
| 3326 | Set theory attempts to reduce the 'is' of predication to mathematics [Benardete,JA] |
| Full Idea: Set theory offers the promise of a complete mathematization of the 'is' of predication. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.13) |
| 3327 | The set of Greeks is included in the set of men, but isn't a member of it [Benardete,JA] |
| Full Idea: Set inclusion is sharply distinguished from set membership (as the set of Greeks is found to be included in, but not a member of, the set of men). | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.13) |
| 10073 | There cannot be a set theory which is complete [Smith,P] |
| Full Idea: By Gödel's First Incompleteness Theorem, there cannot be a negation-complete set theory. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 01.3) | |
| A reaction: This means that we can never prove all the truths of a system of set theory. |
| 3335 | The standard Z-F Intuition version of set theory has about ten agreed axioms [Benardete,JA, by PG] |
| Full Idea: Zermelo proposed seven axioms for set theory, with Fraenkel adding others, to produce the standard Z-F Intuition. | |
| From: report of José A. Benardete (Metaphysics: the logical approach [1989], Ch.17) by PG - Db (ideas) |
| 10616 | Second-order arithmetic can prove new sentences of first-order [Smith,P] |
| Full Idea: Going second-order in arithmetic enables us to prove new first-order arithmetical sentences that we couldn't prove before. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 23.4) | |
| A reaction: The wages of Satan, perhaps. We can prove things about objects by proving things about their properties and sets and functions. Smith says this fact goes all the way up the hierarchy. |
| 9119 | No attempt to deny bivalence has ever been accepted [Sorensen] |
| Full Idea: The history of deviant logics is without a single success. Bivalence has been denied at least since Aristotle, yet no anti-bivalent theory has ever left the philosophical nursery. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], Intro) | |
| A reaction: This is part of a claim that nothing in reality is vague - it is just our ignorance of the truth or falsity of some propositions. Personally I don't see why 'Grandad is bald' has to have a determinate truth value. |
| 9135 | We now see that generalizations use variables rather than abstract entities [Sorensen] |
| Full Idea: As philosophers gradually freed themselves from the assumption that all words are names, ..they realised that generalizations really use variables rather than names of abstract entities. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 8.4) | |
| A reaction: This looks like a key thought in trying to understand abstraction - though I don't think you can shake it off that easily. (For all x)(x-is-a-bird then x-has-wings) seems to require a generalised concept of a bird to give a value to the variable. |
| 10612 | An argument is a 'fixed point' for a function if it is mapped back to itself [Smith,P] |
| Full Idea: If a function f maps the argument a back to a itself, so that f(a) = a, then a is said to be a 'fixed point' for f. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 20.5) |
| 10076 | The 'range' of a function is the set of elements in the output set created by the function [Smith,P] |
| Full Idea: The 'range' of a function is the set of elements in the output set that are values of the function for elements in the original set. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.1) | |
| A reaction: In other words, the range is the set of values that were created by the function. |
| 10605 | Two functions are the same if they have the same extension [Smith,P] |
| Full Idea: We count two functions as being the same if they have the same extension, i.e. if they pair up arguments with values in the same way. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 11.3) | |
| A reaction: So there's only one way to skin a cat in mathematical logic. |
| 10075 | A 'partial function' maps only some elements to another set [Smith,P] |
| Full Idea: A 'partial function' is one which maps only some elements of a domain to elements in another set. For example, the reciprocal function 1/x is not defined for x=0. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.1 n1) |
| 10074 | A 'total function' maps every element to one element in another set [Smith,P] |
| Full Idea: A 'total function' is one which maps every element of a domain to exactly one corresponding value in another set. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.1) |
| 10615 | The Comprehension Schema says there is a property only had by things satisfying a condition [Smith,P] |
| Full Idea: The so-called Comprehension Schema ∃X∀x(Xx ↔ φ(x)) says that there is a property which is had by just those things which satisfy the condition φ. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 22.3) |
| 10595 | A 'theorem' of a theory is a sentence derived from the axioms using the proof system [Smith,P] |
| Full Idea: 'Theorem': given a derivation of the sentence φ from the axioms of the theory T using the background logical proof system, we will say that φ is a 'theorem' of the theory. Standard abbreviation is T |- φ. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 03.4) |
| 10602 | A 'natural deduction system' has no axioms but many rules [Smith,P] |
| Full Idea: A 'natural deduction system' will have no logical axioms but may rules of inference. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 09.1) | |
| A reaction: He contrasts this with 'Hilbert-style systems', which have many axioms but few rules. Natural deduction uses many assumptions which are then discharged, and so tree-systems are good for representing it. |
| 10613 | No nice theory can define truth for its own language [Smith,P] |
| Full Idea: No nice theory can define truth for its own language. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 21.5) | |
| A reaction: This leads on to Tarski's account of truth. |
| 10078 | An 'injective' ('one-to-one') function creates a distinct output element from each original [Smith,P] |
| Full Idea: An 'injective' function is 'one-to-one' - each element of the output set results from a different element of the original set. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.1) | |
| A reaction: That is, two different original elements cannot lead to the same output element. |
| 10077 | A 'surjective' ('onto') function creates every element of the output set [Smith,P] |
| Full Idea: A 'surjective' function is 'onto' - the whole of the output set results from the function being applied to elements of the original set. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.1) |
| 10079 | A 'bijective' function has one-to-one correspondence in both directions [Smith,P] |
| Full Idea: A 'bijective' function has 'one-to-one correspondence' - it is both surjective and injective, so that every element in each of the original and the output sets has a matching element in the other. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.1) | |
| A reaction: Note that 'injective' is also one-to-one, but only in the one direction. |
| 10070 | If everything that a theory proves is true, then it is 'sound' [Smith,P] |
| Full Idea: If everything that a theory proves must be true, then it is a 'sound' theory. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 01.1) |
| 10086 | Soundness is true axioms and a truth-preserving proof system [Smith,P] |
| Full Idea: Soundness is normally a matter of having true axioms and a truth-preserving proof system. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 03.4) | |
| A reaction: The only exception I can think of is if a theory consisted of nothing but the axioms. |
| 10596 | A theory is 'sound' iff every theorem is true (usually from true axioms and truth-preservation) [Smith,P] |
| Full Idea: A theory is 'sound' iff every theorem of it is true (i.e. true on the interpretation built into its language). Soundness is normally a matter of having true axioms and a truth-preserving proof system. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 03.4) |
| 10598 | A theory is 'negation complete' if it proves all sentences or their negation [Smith,P] |
| Full Idea: A theory is 'negation complete' if it decides every sentence of its language (either the sentence, or its negation). | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 03.4) |
| 10597 | 'Complete' applies both to whole logics, and to theories within them [Smith,P] |
| Full Idea: There is an annoying double-use of 'complete': a logic may be semantically complete, but there may be an incomplete theory expressed in it. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 03.4) |
| 10069 | A theory is 'negation complete' if one of its sentences or its negation can always be proved [Smith,P] |
| Full Idea: Logicians say that a theory T is '(negation) complete' if, for every sentence φ in the language of the theory, either φ or ¬φ is deducible in T's proof system. If this were the case, then truth could be equated with provability. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 01.1) | |
| A reaction: The word 'negation' seems to be a recent addition to the concept. Presumable it might be the case that φ can always be proved, but not ¬φ. |
| 10609 | Two routes to Incompleteness: semantics of sound/expressible, or syntax of consistency/proof [Smith,P] |
| Full Idea: There are two routes to Incompleteness results. One goes via the semantic assumption that we are dealing with sound theories, using a result about what they can express. The other uses the syntactic notion of consistency, with stronger notions of proof. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 18.1) |
| 10080 | 'Effective' means simple, unintuitive, independent, controlled, dumb, and terminating [Smith,P] |
| Full Idea: An 'effectively decidable' (or 'computable') algorithm will be step-by-small-step, with no need for intuition, or for independent sources, with no random methods, possible for a dumb computer, and terminates in finite steps. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.2) | |
| A reaction: [a compressed paragraph] |
| 10087 | A theory is 'decidable' if all of its sentences could be mechanically proved [Smith,P] |
| Full Idea: A theory is 'decidable' iff there is a mechanical procedure for determining whether any sentence of its language can be proved. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 03.4) | |
| A reaction: Note that it doesn't actually have to be proved. The theorems of the theory are all effectively decidable. |
| 10088 | Any consistent, axiomatized, negation-complete formal theory is decidable [Smith,P] |
| Full Idea: Any consistent, axiomatized, negation-complete formal theory is decidable. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 03.6) |
| 10081 | A set is 'enumerable' is all of its elements can result from a natural number function [Smith,P] |
| Full Idea: A set is 'enumerable' iff either the set is empty, or there is a surjective function to the set from the set of natural numbers, so that the set is in the range of that function. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.3) |
| 10083 | A set is 'effectively enumerable' if a computer could eventually list every member [Smith,P] |
| Full Idea: A set is 'effectively enumerable' if an (idealised) computer could be programmed to generate a list of its members such that any member will eventually be mentioned (even if the list is empty, or without end, or contains repetitions). | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.4) |
| 10084 | A finite set of finitely specifiable objects is always effectively enumerable (e.g. primes) [Smith,P] |
| Full Idea: A finite set of finitely specifiable objects is always effectively enumerable (for example, the prime numbers). | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.4) |
| 10085 | The set of ordered pairs of natural numbers <i,j> is effectively enumerable [Smith,P] |
| Full Idea: The set of ordered pairs of natural numbers (i,j) is effectively enumerable, as proven by listing them in an array (across: <0,0>, <0,1>, <0,2> ..., and down: <0,0>, <1,0>, <2,0>...), and then zig-zagging. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 02.5) |
| 10601 | The thorems of a nice arithmetic can be enumerated, but not the truths (so they're diffferent) [Smith,P] |
| Full Idea: The theorems of any properly axiomatized theory can be effectively enumerated. However, the truths of any sufficiently expressive arithmetic can't be effectively enumerated. Hence the theorems and truths of arithmetic cannot be the same. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 05 Intro) |
| 10600 | Being 'expressible' depends on language; being 'capture/represented' depends on axioms and proof system [Smith,P] |
| Full Idea: Whether a property is 'expressible' in a given theory depends on the richness of the theory's language. Whether the property can be 'captured' (or 'represented') by the theory depends on the richness of the axioms and proof system. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 04.7) |
| 9125 | Denying problems, or being romantically defeated by them, won't make them go away [Sorensen] |
| Full Idea: An unsolvable problem is still a problem, despite Wittgenstein's view that there are no genuine philosophical problems, and Kant's romantic defeatism in his treatment of the antinomies of pure reason. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 4.3) | |
| A reaction: I like the spin put on Kant, that he is a romantic in his defeatism. He certainly seems reluctant to slash at the Gordian knot, e.g. by being a bit more drastically sceptical about free will. |
| 9137 | Banning self-reference would outlaw 'This very sentence is in English' [Sorensen] |
| Full Idea: The old objection to the ban on self-reference is that it is too broad; it bans innocent sentences such as 'This very sentence is in English'. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 11.1) | |
| A reaction: Tricky. What is the sigificant difference between 'this sentence is in English' and 'this sentence is a lie'? The first concerns context and is partly metalinguistic. The second concerns semantics and truth. Concept and content.. |
| 3332 | Greeks saw the science of proportion as the link between geometry and arithmetic [Benardete,JA] |
| Full Idea: The Greeks saw the independent science of proportion as the link between geometry and arithmetic. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.15) |
| 10599 | For primes we write (x not= 1 ∧ ∀u∀v(u x v = x → (u = 1 ∨ v = 1))) [Smith,P] |
| Full Idea: For prime numbers we write (x not= 1 ∧ ∀u∀v(u x v = x → (u = 1 ∨ v = 1))). That is, the only way to multiply two numbers and a get a prime is if one of them is 1. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 04.5) |
| 3330 | Negatives, rationals, irrationals and imaginaries are all postulated to solve baffling equations [Benardete,JA] |
| Full Idea: The Negative numbers are postulated (magic word) to solve x=5-8, Rationals postulated to solve 2x=3, Irrationals for x-squared=2, and Imaginaries for x-squared=-1. (…and Zero for x=5-5) …and x/0 remains eternally open. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.14) |
| 3337 | Natural numbers are seen in terms of either their ordinality (Peano), or cardinality (set theory) [Benardete,JA] |
| Full Idea: One approaches the natural numbers in terms of either their ordinality (Peano), or cardinality (set theory). | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.17) |
| 10610 | The reals contain the naturals, but the theory of reals doesn't contain the theory of naturals [Smith,P] |
| Full Idea: It has been proved (by Tarski) that the real numbers R is a complete theory. But this means that while the real numbers contain the natural numbers, the pure theory of real numbers doesn't contain the theory of natural numbers. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 18.2) |
| 10619 | The truths of arithmetic are just true equations and their universally quantified versions [Smith,P] |
| Full Idea: The truths of arithmetic are just the true equations involving particular numbers, and universally quantified versions of such equations. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 27.7) | |
| A reaction: Must each equation be universally quantified? Why can't we just universally quantify over the whole system? |
| 10618 | All numbers are related to zero by the ancestral of the successor relation [Smith,P] |
| Full Idea: All numbers are related to zero by the ancestral of the successor relation. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 23.5) | |
| A reaction: The successor relation only ties a number to the previous one, not to the whole series. Ancestrals are a higher level of abstraction. |
| 10608 | The number of Fs is the 'successor' of the Gs if there is a single F that isn't G [Smith,P] |
| Full Idea: The number of Fs is the 'successor' of the number of Gs if there is an object which is an F, and the remaining things that are F but not identical to the object are equinumerous with the Gs. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 14.1) |
| 10849 | Baby arithmetic covers addition and multiplication, but no general facts about numbers [Smith,P] |
| Full Idea: Baby Arithmetic 'knows' the addition of particular numbers and multiplication, but can't express general facts about numbers, because it lacks quantification. It has a constant '0', a function 'S', and functions '+' and 'x', and identity and negation. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 08.1) |
| 10850 | Baby Arithmetic is complete, but not very expressive [Smith,P] |
| Full Idea: Baby Arithmetic is negation complete, so it can prove every claim (or its negation) that it can express, but it is expressively extremely impoverished. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 08.3) |
| 10852 | Robinson Arithmetic (Q) is not negation complete [Smith,P] |
| Full Idea: Robinson Arithmetic (Q) is not negation complete | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 08.4) |
| 10851 | Robinson Arithmetic 'Q' has basic axioms, quantifiers and first-order logic [Smith,P] |
| Full Idea: We can beef up Baby Arithmetic into Robinson Arithmetic (referred to as 'Q'), by restoring quantifiers and variables. It has seven generalised axioms, plus standard first-order logic. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 08.3) |
| 10068 | Natural numbers have zero, unique successors, unending, no circling back, and no strays [Smith,P] |
| Full Idea: The sequence of natural numbers starts from zero, and each number has just one immediate successor; the sequence continues without end, never circling back on itself, and there are no 'stray' numbers, lurking outside the sequence. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 01.1) | |
| A reaction: These are the characteristics of the natural numbers which have to be pinned down by any axiom system, such as Peano's, or any more modern axiomatic structures. We are in the territory of Gödel's theorems. |
| 10603 | The logic of arithmetic must quantify over properties of numbers to handle induction [Smith,P] |
| Full Idea: If the logic of arithmetic doesn't have second-order quantifiers to range over properties of numbers, how can it handle induction? | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 10.1) |
| 10848 | Multiplication only generates incompleteness if combined with addition and successor [Smith,P] |
| Full Idea: Multiplication in itself isn't is intractable. In 1929 Skolem showed a complete theory for a first-order language with multiplication but lacking addition (or successor). Multiplication together with addition and successor produces incompleteness. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 10.7 n8) |
| 10604 | Incompleteness results in arithmetic from combining addition and successor with multiplication [Smith,P] |
| Full Idea: Putting multiplication together with addition and successor in the language of arithmetic produces incompleteness. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 10.7) | |
| A reaction: His 'Baby Arithmetic' has all three and is complete, but lacks quantification (p.51) |
| 3310 | If slowness is a property of walking rather than the walker, we must allow that events exist [Benardete,JA] |
| Full Idea: Once we conceded that Tom can walk slowly or quickly, and that the slowness and quickness is a property of the walking and not of Tom, we can hardly refrain from quantifying over events (such as 'a walking') in our ontology. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 6) |
| 12793 | Early pre-Socratics had a mass-noun ontology, which was replaced by count-nouns [Benardete,JA] |
| Full Idea: With their 'mass-noun' ontologies, the early pre-Socratics were blind to plurality ...but the count-noun ontologists came to dominate the field forever after. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 6) | |
| A reaction: The mass-nouns are such things as earth, air, fire and water. This is a very interesting historical observation (cited by Laycock). Our obsession with identity seems tied to formal logic. There is a whole other worldview waiting out there. |
| 9116 | Vague words have hidden boundaries [Sorensen] |
| Full Idea: Vague words have hidden boundaries. The subtraction of a single grain of sand might turn a heap into a non-heap. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], Intro) | |
| A reaction: The first sentence could be the slogan for the epistemic view of vagueness. The opposite view is Sainsbury's - that vague words are those which do not have any boundaries. Sorensen admits his view is highly counterintuitive. I think I prefer Sainsbury. |
| 10617 | The 'ancestral' of a relation is a new relation which creates a long chain of the original relation [Smith,P] |
| Full Idea: The 'ancestral' of a relation is that relation which holds when there is an indefinitely long chain of things having the initial relation. | |
| From: Peter Smith (Intro to Gödel's Theorems [2007], 23.5) | |
| A reaction: The standard example is spotting the relation 'ancestor' from the receding relation 'parent'. This is a sort of abstraction derived from a relation which is not equivalent (parenthood being transitive but not reflexive). The idea originated with Frege. |
| 3353 | If there is no causal interaction with transcendent Platonic objects, how can you learn about them? [Benardete,JA] |
| Full Idea: How can you learn of the existence of transcendent Platonic objects if there is no causal interaction with them? | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.22) |
| 9132 | An offer of 'free coffee or juice' could slowly shift from exclusive 'or' to inclusive 'or' [Sorensen] |
| Full Idea: Sometimes an exclusive 'or' gradually develops into an inclusive 'or'. A restaurant offers 'free coffee or juice'. The customers ask for both, and gradually they are given it, first as a courtesy, and eventually as an expectation. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 7.2) | |
| A reaction: [compressed] A very nice example - of the rot of vagueness even seeping into the basic logical connectives. We don't have to accept it, though. Each instance of usage of 'or', by manager or customer, might be clearly one or the other. |
| 3304 | Why should packed-together particles be a thing (Mt Everest), but not scattered ones? [Benardete,JA] |
| Full Idea: Why suppose these particles packed together constitute a macro-entity (namely, Mt Everest), whereas those, of equal number, scattered around, fail to add up to anything beyond themselves? | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 2) |
| 3350 | Could a horse lose the essential property of being a horse, and yet continue to exist? [Benardete,JA] |
| Full Idea: Is being a horse an essential property of a horse? Can we so much as conceive the abstract possibility of a horse's ceasing to be a horse even while continuing to exist? | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.20) |
| 3309 | If a soldier continues to exist after serving as a soldier, does the wind cease to exist after it ceases to blow? [Benardete,JA] |
| Full Idea: If a soldier need not cease to exist merely because he ceases to be a soldier, there is room to doubt that the wind ceases to exist when it ceases to be a wind. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 6) |
| 3351 | One can step into the same river twice, but not into the same water [Benardete,JA] |
| Full Idea: One can step into the same river twice, but one must not expect to step into the same water. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.21) |
| 3314 | Absolutists might accept that to exist is relative, but relative to what? How about relative to itself? [Benardete,JA] |
| Full Idea: With the thesis that to be as such is to be relative, the absolutist may be found to concur, but the issue turns on what it might be that a thing is supposed to be relative to. Why not itself? | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 8) |
| 3323 | Maybe self-identity isn't existence, if Pegasus can be self-identical but non-existent [Benardete,JA] |
| Full Idea: 'Existence' can't be glossed as self-identical (critics say) because Pegasus, even while being self-identical, fails to exist. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.11) |
| 3306 | The clearest a priori knowledge is proving non-existence through contradiction [Benardete,JA] |
| Full Idea: One proves non-existence (e.g. of round squares) by using logic to derive a contradiction from the concept; it is precisely here, in such proofs, that we find the clearest example of a priori knowledge. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 4) |
| 9128 | It is propositional attitudes which can be a priori, not the propositions themselves [Sorensen] |
| Full Idea: The primary bearer of apriority is the propositional attitude (believing, knowing, guessing and so on) rather than the proposition itself. A proposition could be a priori to homo sapiens but a posteriori to Neandethals. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 6.3) | |
| A reaction: A putative supreme being is quite useful here, who might even see the necessity of Arsenal beating Manchester United next Saturday. Unlike infants, adults know a priori that square pegs won't fit round holes. |
| 9130 | Attributing apriority to a proposition is attributing a cognitive ability to someone [Sorensen] |
| Full Idea: Every attribution of apriority to a proposition is tacitly an attribution of a cognitive ability to some thinker. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 6.3) | |
| A reaction: The ability would include a range of background knowledge, as well as a sheer power of intellect. If you know all of Euclid's theorems, you will spot facts about geometrical figues quicker than me. His point is important. |
| 3349 | If we know truths about prime numbers, we seem to have synthetic a priori knowledge of Platonic objects [Benardete,JA] |
| Full Idea: Assume that we know to be true propositions of the form 'There are exactly x prime numbers between y and z', and synthetic a priori truths about Platonic objects are delivered to us on a silver platter. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.18) |
| 3341 | Logical positivism amounts to no more than 'there is no synthetic a priori' [Benardete,JA] |
| Full Idea: Logical positivism has been concisely summarised as 'there is no synthetic a priori'. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.18) |
| 3344 | Assertions about existence beyond experience can only be a priori synthetic [Benardete,JA] |
| Full Idea: No one thinks that the proposition that something exists that transcends all possible experience harbours a logical inconsistency. Its denial cannot therefore be an analytic proposition, so it must be synthetic, though only knowable on a priori grounds. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.18) |
| 3345 | Appeals to intuition seem to imply synthetic a priori knowledge [Benardete,JA] |
| Full Idea: Appeals to intuition - no matter how informal - can hardly fail to smack of the synthetic a priori. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.18) |
| 9118 | The colour bands of the spectrum arise from our biology; they do not exist in the physics [Sorensen] |
| Full Idea: The bands of colour in a colour spectrum do not correspond to objective discontinuities in light wavelengths. These apparently external bands arise from our biology rather than simple physics. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], Intro) | |
| A reaction: If any more arguments are needed to endorse the fact that some qualities are clearly secondary (and, to my amazement, such arguments seem to be very much needed), I would take this to be one of the final conclusive pieces of evidence. |
| 9124 | We are unable to perceive a nose (on the back of a mask) as concave [Sorensen] |
| Full Idea: The human perceptual system appears unable to represent a nose as concave rather than convex. If you look at the concave side of a mask, you see the features as convex. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 4.3) | |
| A reaction: I don't think that is quite true. You wouldn't put a mask on if you thought it was convex. It is usually when seen at a distance with strong cross-lighting that the effect emerges. Nevertheless, it is an important point. |
| 9126 | Bayesians build near-certainty from lots of reasonably probable beliefs [Sorensen] |
| Full Idea: Bayesians demonstrate that a self-correcting agent can build an imposing edifice of near-certain knowledge from numerous beliefs that are only slightly more probable than not. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 6.1) | |
| A reaction: This strikes me as highly significant for the coherence account of justification, even if one is sceptical about the arithmetical approach to belief of Bayesianism. It seems obvious that lots of quite likely facts build towards certainty, Watson. |
| 9121 | Illusions are not a reason for skepticism, but a source of interesting scientific information [Sorensen] |
| Full Idea: Philosophers tend to associate illusions with skepticism. But since illusions are signs of modular construction, they are actually reason for scientific hope. Illusions have been very useful in helping us to understand vision. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 1.4) | |
| A reaction: This is a nice reversal of the usual view. If I see double, it reveals to me that my eyes are not aligned properly. Anyone led to scepticism by illusions should pay more attention to themselves, and less to the reality they hope to know directly. |
| 9134 | The negation of a meaningful sentence must itself be meaningful [Sorensen] |
| Full Idea: The negation of any meaningful sentence must itself be meaningful. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 8.1) | |
| A reaction: Nice. Compare 'there is another prime number beyond the highest one we have found' with its negation. The first seems verifiable in principle, but the second one doesn't. So the verificationist must deny Sorensen's idea? |
| 9133 | Propositions are what settle problems of ambiguity in sentences [Sorensen] |
| Full Idea: Propositions play the role of dis-ambiguators; they are the things between which utterances are ambiguous. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 7.7) | |
| A reaction: I have become a great fan of propositions, and I think this is one of the key reasons for believing in them. The proposition is what we attempt to pin down when asked 'what exactly did you mean by what you just said?' |
| 9129 | I can buy any litre of water, but not every litre of water [Sorensen] |
| Full Idea: I am entitled to buy any litre of water, but I am not entitled to buy every litre of water. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 6.3) | |
| A reaction: A decent social system must somehow draw a line between buying up all the water and buying up all the paintings of Vermeer. Even the latter seems wicked, but it is hard to pin down the reason. |
| 3334 | Rationalists see points as fundamental, but empiricists prefer regions [Benardete,JA] |
| Full Idea: Rationalists have been happier with an ontology of points, and empiricists with an ontology of regions. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch.16) |
| 9122 | God cannot experience unwanted pain, so God cannot understand human beings [Sorensen] |
| Full Idea: Theologians worry that God may be an alien being. God cannot feel pain since pain is endured against one's will. God is all powerful and suffers nothing against His Will. To understand pain, one must experience pain. So God's power walls him off from us. | |
| From: Roy Sorensen (Vagueness and Contradiction [2001], 3.2) | |
| A reaction: I can't think of a good theological reply to this. God, and Jesus too (presumably), can only experience pain if they volunteer for it. It is inconceivable that they could be desperate for it to stop, but were unable to achieve that. |
| 3308 | In the ontological argument a full understanding of the concept of God implies a contradiction in 'There is no God' [Benardete,JA] |
| Full Idea: In the ontological argument a deep enough understanding of the very concept of God allows one to derive by logic a contradiction from the statement 'There is no God'. | |
| From: José A. Benardete (Metaphysics: the logical approach [1989], Ch. 4) |