76 ideas
| 9955 | Contextual definitions replace a complete sentence containing the expression [George/Velleman] |
| Full Idea: A contextual definition shows how to analyse an expression in situ, by replacing a complete sentence (of a particular form) in which the expression occurs by another in which it does not. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.2) | |
| A reaction: This is a controversial procedure, which (according to Dummett) Frege originally accepted, and later rejected. It might not be the perfect definition that replacing just the expression would give you, but it is a promising step. |
| 10031 | Impredicative definitions quantify over the thing being defined [George/Velleman] |
| Full Idea: When a definition contains a quantifier whose range includes the very entity being defined, the definition is said to be 'impredicative'. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.2) | |
| A reaction: Presumably they are 'impredicative' because they do not predicate a new quality in the definiens, but make use of the qualities already known. |
| 9449 | The plausible Barcan formula implies modality in the actual world [Bird] |
| Full Idea: Modality in the actual world is the import of the Barcan formula, and there are good reasons for accepting the Barcan formula. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 1.2) | |
| A reaction: If you thought logic was irrelevant to metaphysics, this should make you think twice. |
| 10098 | The 'power set' of A is all the subsets of A [George/Velleman] |
| Full Idea: The 'power set' of A is all the subsets of A. P(A) = {B : B ⊆ A}. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) |
| 10099 | The 'ordered pair' <a, b>, for two sets a and b, is the set {{a, b},{a}} [George/Velleman] |
| Full Idea: The 'ordered pair' <a, b>, for two sets a and b, is the set {{a, b},{a}}. The existence of this set is guaranteed by three applications of the Axiom of Pairing. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: See Idea 10100 for the Axiom of Pairing. |
| 10101 |
Cartesian Product A x B: the set of all ordered pairs |
| Full Idea: The 'Cartesian Product' of any two sets A and B is the set of all ordered pairs <a, b> in which a ∈ A and b ∈ B, and it is denoted as A x B. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) |
| 10103 | Grouping by property is common in mathematics, usually using equivalence [George/Velleman] |
| Full Idea: The idea of grouping together objects that share some property is a common one in mathematics, ...and the technique most often involves the use of equivalence relations. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) |
| 10104 | 'Equivalence' is a reflexive, symmetric and transitive relation; 'same first letter' partitions English words [George/Velleman] |
| Full Idea: A relation is an equivalence relation if it is reflexive, symmetric and transitive. The 'same first letter' is an equivalence relation on the set of English words. Any relation that puts a partition into clusters will be equivalence - and vice versa. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: This is a key concept in the Fregean strategy for defining numbers. |
| 10096 | Even the elements of sets in ZFC are sets, resting on the pure empty set [George/Velleman] |
| Full Idea: ZFC is a theory concerned only with sets. Even the elements of all of the sets studied in ZFC are also sets (whose elements are also sets, and so on). This rests on one clearly pure set, the empty set Φ. ..Mathematics only needs pure sets. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: This makes ZFC a much more metaphysically comfortable way to think about sets, because it can be viewed entirely formally. It is rather hard to disentangle a chair from the singleton set of that chair. |
| 10097 | Axiom of Extensionality: for all sets x and y, if x and y have the same elements then x = y [George/Velleman] |
| Full Idea: The Axiom of Extensionality says that for all sets x and y, if x and y have the same elements then x = y. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: This seems fine in pure set theory, but hits the problem of renates and cordates in the real world. The elements coincide, but the axiom can't tell you why they coincide. |
| 10100 | Axiom of Pairing: for all sets x and y, there is a set z containing just x and y [George/Velleman] |
| Full Idea: The Axiom of Pairing says that for all sets x and y, there is a set z containing x and y, and nothing else. In symbols: ∀x∀y∃z∀w(w ∈ z ↔ (w = x ∨ w = y)). | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: See Idea 10099 for an application of this axiom. |
| 17900 | The Axiom of Reducibility made impredicative definitions possible [George/Velleman] |
| Full Idea: The Axiom of Reducibility ...had the effect of making impredicative definitions possible. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) |
| 10109 | ZFC can prove that there is no set corresponding to the concept 'set' [George/Velleman] |
| Full Idea: Sets, unlike extensions, fail to correspond to all concepts. We can prove in ZFC that there is no set corresponding to the concept 'set' - that is, there is no set of all sets. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.4) | |
| A reaction: This is rather an important point for Frege. However, all concepts have extensions, but they may be proper classes, rather than precisely defined sets. |
| 10108 | As a reduction of arithmetic, set theory is not fully general, and so not logical [George/Velleman] |
| Full Idea: The problem with reducing arithmetic to ZFC is not that this theory is inconsistent (as far as we know it is not), but rather that is not completely general, and for this reason not logical. For example, it asserts the existence of sets. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.4) | |
| A reaction: Note that ZFC has not been proved consistent. |
| 10111 | Asserting Excluded Middle is a hallmark of realism about the natural world [George/Velleman] |
| Full Idea: A hallmark of our realist stance towards the natural world is that we are prepared to assert the Law of Excluded Middle for all statements about it. For all statements S, either S is true, or not-S is true. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.4) | |
| A reaction: Personally I firmly subscribe to realism, so I suppose I must subscribe to Excluded Middle. ...Provided the statement is properly formulated. Or does liking excluded middle lead me to realism? |
| 10129 | A 'model' is a meaning-assignment which makes all the axioms true [George/Velleman] |
| Full Idea: A 'model' of a theory is an assignment of meanings to the symbols of its language which makes all of its axioms come out true. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.7) | |
| A reaction: If the axioms are all true, and the theory is sound, then all of the theorems will also come out true. |
| 10105 | Differences between isomorphic structures seem unimportant [George/Velleman] |
| Full Idea: Mathematicians tend to regard the differences between isomorphic mathematical structures as unimportant. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: This seems to be a pointer towards Structuralism as the underlying story in mathematics. The intrinsic character of so-called 'objects' seems unimportant. How theories map onto one another (and onto the world?) is all that matters? |
| 10119 | Consistency is a purely syntactic property, unlike the semantic property of soundness [George/Velleman] |
| Full Idea: Consistency is a purely syntactic property, unlike the semantic property of soundness. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.6) |
| 10126 | A 'consistent' theory cannot contain both a sentence and its negation [George/Velleman] |
| Full Idea: If there is a sentence such that both the sentence and its negation are theorems of a theory, then the theory is 'inconsistent'. Otherwise it is 'consistent'. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.7) |
| 10120 | Soundness is a semantic property, unlike the purely syntactic property of consistency [George/Velleman] |
| Full Idea: Soundness is a semantic property, unlike the purely syntactic property of consistency. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.6) |
| 10127 | A 'complete' theory contains either any sentence or its negation [George/Velleman] |
| Full Idea: If there is a sentence such that neither the sentence nor its negation are theorems of a theory, then the theory is 'incomplete'. Otherwise it is 'complete'. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.7) | |
| A reaction: Interesting questions are raised about undecidable sentences, irrelevant sentences, unknown sentences.... |
| 10106 | Rational numbers give answers to division problems with integers [George/Velleman] |
| Full Idea: We can think of rational numbers as providing answers to division problems involving integers. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: Cf. Idea 10102. |
| 10102 | The integers are answers to subtraction problems involving natural numbers [George/Velleman] |
| Full Idea: In defining the integers in set theory, our definition will be motivated by thinking of the integers as answers to subtraction problems involving natural numbers. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: Typical of how all of the families of numbers came into existence; they are 'invented' so that we can have answers to problems, even if we can't interpret the answers. It it is money, we may say the minus-number is a 'debt', but is it? Cf Idea 10106. |
| 10107 | Real numbers provide answers to square root problems [George/Velleman] |
| Full Idea: One reason for introducing the real numbers is to provide answers to square root problems. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: Presumably the other main reasons is to deal with problems of exact measurement. It is interesting that there seem to be two quite distinct reasons for introducing the reals. Cf. Ideas 10102 and 10106. |
| 9946 | Logicists say mathematics is applicable because it is totally general [George/Velleman] |
| Full Idea: The logicist idea is that if mathematics is logic, and logic is the most general of disciplines, one that applies to all rational thought regardless of its content, then it is not surprising that mathematics is widely applicable. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.2) | |
| A reaction: Frege was keen to emphasise this. You are left wondering why pure logic is applicable to the physical world. The only account I can give is big-time Platonism, or Pythagoreanism. Logic reveals the engine-room of nature, where the design is done. |
| 10125 | The classical mathematician believes the real numbers form an actual set [George/Velleman] |
| Full Idea: Unlike the intuitionist, the classical mathematician believes in an actual set that contains all the real numbers. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.6) |
| 17899 | Second-order induction is stronger as it covers all concepts, not just first-order definable ones [George/Velleman] |
| Full Idea: The first-order version of the induction axiom is weaker than the second-order, because the latter applies to all concepts, but the first-order applies only to concepts definable by a formula in the first-order language of number theory. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.7 n7) |
| 10128 | The Incompleteness proofs use arithmetic to talk about formal arithmetic [George/Velleman] |
| Full Idea: The idea behind the proofs of the Incompleteness Theorems is to use the language of Peano Arithmetic to talk about the formal system of Peano Arithmetic itself. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.7) | |
| A reaction: The mechanism used is to assign a Gödel Number to every possible formula, so that all reasonings become instances of arithmetic. |
| 17902 | A successor is the union of a set with its singleton [George/Velleman] |
| Full Idea: For any set x, we define the 'successor' of x to be the set S(x) = x U {x}. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: This is the Fregean approach to successor, where the Dedekind approach takes 'successor' to be a primitive. Frege 1884:§76. |
| 10133 | Frege's Theorem shows the Peano Postulates can be derived from Hume's Principle [George/Velleman] |
| Full Idea: The derivability of Peano's Postulates from Hume's Principle in second-order logic has been dubbed 'Frege's Theorem', (though Frege would not have been interested, because he didn't think Hume's Principle gave an adequate definition of numebrs). | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.8 n1) | |
| A reaction: Frege said the numbers were the sets which were the extensions of the sets created by Hume's Principle. |
| 10130 | Set theory can prove the Peano Postulates [George/Velleman] |
| Full Idea: The Peano Postulates can be proven in ZFC. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.7) |
| 10089 | Talk of 'abstract entities' is more a label for the problem than a solution to it [George/Velleman] |
| Full Idea: One might well wonder whether talk of abstract entities is less a solution to the empiricist's problem of how a priori knowledge is possible than it is a label for the problem. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Intro) | |
| A reaction: This pinpoints my view nicely. What the platonist postulates is remote, bewildering, implausible and useless! |
| 10131 | If mathematics is not about particulars, observing particulars must be irrelevant [George/Velleman] |
| Full Idea: As, in the logicist view, mathematics is about nothing particular, it is little wonder that nothing in particular needs to be observed in order to acquire mathematical knowledge. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002]) | |
| A reaction: At the very least we can say that no one would have even dreamt of the general system of arithmetic is they hadn't had experience of the particulars. Frege thought generality ensured applicability, but extreme generality might entail irrelevance. |
| 17901 | Type theory prohibits (oddly) a set containing an individual and a set of individuals [George/Velleman] |
| Full Idea: If a is an individual and b is a set of individuals, then in the theory of types we cannot talk about the set {a,b}, since it is not an individual or a set of individuals, ...but it is hard to see what harm can come from it. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) |
| 10092 | In the unramified theory of types, the types are objects, then sets of objects, sets of sets etc. [George/Velleman] |
| Full Idea: In the unramified theory of types, all objects are classified into a hierarchy of types. The lowest level has individual objects that are not sets. Next come sets whose elements are individuals, then sets of sets, etc. Variables are confined to types. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: The objects are Type 0, the basic sets Type 1, etc. |
| 10094 | The theory of types seems to rule out harmless sets as well as paradoxical ones. [George/Velleman] |
| Full Idea: The theory of types seems to rule out harmless sets as well as paradoxical ones. If a is an individual and b is a set of individuals, then in type theory we cannot talk about the set {a,b}. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: Since we cheerfully talk about 'Cicero and other Romans', this sounds like a rather disasterous weakness. |
| 10095 | Type theory has only finitely many items at each level, which is a problem for mathematics [George/Velleman] |
| Full Idea: A problem with type theory is that there are only finitely many individuals, and finitely many sets of individuals, and so on. The hierarchy may be infinite, but each level is finite. Mathematics required an axiom asserting infinitely many individuals. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.3) | |
| A reaction: Most accounts of mathematics founder when it comes to infinities. Perhaps we should just reject them? |
| 10134 | Much infinite mathematics can still be justified finitely [George/Velleman] |
| Full Idea: It is possible to use finitary reasoning to justify a significant part of infinitary mathematics. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.8) | |
| A reaction: This might save Hilbert's project, by gradually accepting into the fold all the parts which have been giving a finitist justification. |
| 10114 | Bounded quantification is originally finitary, as conjunctions and disjunctions [George/Velleman] |
| Full Idea: In the first instance all bounded quantifications are finitary, for they can be viewed as abbreviations for conjunctions and disjunctions. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.6) | |
| A reaction: This strikes me as quite good support for finitism. The origin of a concept gives a good guide to what it really means (not a popular view, I admit). When Aristotle started quantifying, I suspect of he thought of lists, not totalities. |
| 10123 | The intuitionists are the idealists of mathematics [George/Velleman] |
| Full Idea: The intuitionists are the idealists of mathematics. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.6) |
| 10124 | Gödel's First Theorem suggests there are truths which are independent of proof [George/Velleman] |
| Full Idea: For intuitionists, truth is not independent of proof, but this independence is precisely what seems to be suggested by Gödel's First Incompleteness Theorem. | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.8) | |
| A reaction: Thus Gödel was worse news for the Intuitionists than he was for Hilbert's Programme. Gödel himself responded by becoming a platonist about his unprovable truths. |
| 9501 | If all existents are causally active, that excludes abstracta and causally isolated objects [Bird] |
| Full Idea: If one says that 'everything that exists is causally active', that rules out abstracta (notably sets and numbers), and it rules out objects that are causally isolated. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 5.5) | |
| A reaction: I like the principle. I take abstracta to be brain events, so they are causally active, within highly refined and focused brains, and if your physics is built on the notion of fields then I would think a 'causally isolated' object incoherent. |
| 9500 | If naturalism refers to supervenience, that leaves necessary entities untouched [Bird] |
| Full Idea: If one's naturalistic principles are formulated in terms of supervenience, then necessary entities are left untouched. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 5.5) | |
| A reaction: I take this to be part of the reason why some people like supervenience - that it leaves a pure 'space of reasons' which is unreachable from the flesh and blood inside a cranium. Personall I like the space of reasons, but I drop the 'pure'. |
| 9502 | There might be just one fundamental natural property [Bird] |
| Full Idea: The thought that there might be just one fundamental natural property is not that strange. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 6.3) | |
| A reaction: A nice variation on the Parmenides idea that only the One exists. Bird's point would refer to a possible unification of modern physics. We see, for example, the forces of electricity and of magnetism turning out to be the same force. |
| 9477 | Categorical properties are not modally fixed, but change across possible worlds [Bird] |
| Full Idea: Categorical properties do not have their dispositional characters modally fixed, but may change their dispositional characters (and their causal and nomic behaviour more generally) across different worlds. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.1) | |
| A reaction: This is the key ground for Bird's praiseworth opposition to categorical propertie. I take it to be a nonsense to call the category in which we place something a 'property' of that thing. A confusion of thought with reality. |
| 9490 | The categoricalist idea is that a property is only individuated by being itself [Bird] |
| Full Idea: In the categoricalist view, the essential properties of a natural property are limited to its essentially being itself and not some distinct property. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 4.1) | |
| A reaction: He associates this view with Lewis (modern regularity view) and Armstrong (nomic necessitation), and launches a splendid attack against it. I have always laughed at the idea that 'being Socrates' was one of the properties of Socrates. |
| 9495 | If we abstractly define a property, that doesn't mean some object could possess it [Bird] |
| Full Idea: The possibility of abstract definition does not show that we have defined a property that we can know, independently of any theory, that it is physically possible for some object to possess. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 4.2.3.1) | |
| A reaction: This is a naturalist resisting the idea that there is no more to a property than set-membership. I strongly agree. We need a firm notion of properties as features of the actual world; anything else should be called something like 'categorisations'. |
| 9492 | Categoricalists take properties to be quiddities, with no essential difference between them [Bird] |
| Full Idea: The categoricalist conception of properties takes them to be quiddities, which are primitive identities between fundamental qualities, having no difference with regard to their essence. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 4.5) | |
| A reaction: Compare 'haecceitism' about indentity of objects, though 'quidditism' sounds even less plausible. Bird attributes this view to Lewis and Armstrong, and makes it sound well daft. |
| 9503 | To name an abundant property is either a Fregean concept, or a simple predicate [Bird] |
| Full Idea: It isn't clear what it is to name an abundant property. One might reify them, as akin to Fregean concepts, or it might be equivalent to a simple predication. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 7.1.2) | |
| A reaction: 'Fregean concepts' would make them functions that purely link things (hence relational?). One suspects that people who actually treat abundant properties as part of their ontology (Lewis) are confusing natural properties with predicates. |
| 14540 | Only real powers are fundamental [Bird, by Mumford/Anjum] |
| Full Idea: Bird says only real powers are fundamental. | |
| From: report of Alexander Bird (Nature's Metaphysics [2007]) by S.Mumford/R.Lill Anjum - Getting Causes from Powers 1.5 | |
| A reaction: They disagree, and want higher-level properties in their ontology. I'm with Bird, except that something must exist to have the powers. Powers are fundamental to all the activity of nature, and are intrinsic to the stuff which constitutes nature. |
| 9450 | If all properties are potencies, and stimuli and manifestation characterise them, there is a regress [Bird] |
| Full Idea: Potencies are characterized in terms of their stimulus and manifestation properties, then if potencies are the only properties then these properties are also potencies, and must be characterized by yet further properties, leading to a vicious regress. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 1.2) | |
| A reaction: This is cited as the most popular objection to the dispositional account of properties. |
| 9498 | The essence of a potency involves relations, e.g. mass, to impressed force and acceleration [Bird] |
| Full Idea: The essence of a potency involves a relation to something else; if inertial mass is a potency then its essence involves a relation to a stimulus property (impressed force) and a manifestation property (acceleration). | |
| From: Alexander Bird (Nature's Metaphysics [2007], 5.3.3) | |
| A reaction: It doesn't seem quite right to say that the relations are part of the essence, if they might not occur, but some other relations might happen in their place. An essence is what makes a relation possible (like being good-looking). |
| 9474 | A disposition is finkish if a time delay might mean the manifestation fizzles out [Bird] |
| Full Idea: Finkish dispositions arise because the time delay between stimulus and manifestation provides an opportunity for the disposition to go out of existence and so halt the process that would bring about the manifestation. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 2.2.3) | |
| A reaction: This is a problem for the conditional analysis of dispositions; there may be a disposition, but it never reaches manifestation. Bird rightly points us towards actual powers rather than dispositions that need manifestation. |
| 9475 | A robust pot attached to a sensitive bomb is not fragile, but if struck it will easily break [Bird] |
| Full Idea: If a robust iron pot is attached to a bomb with a sensitive detonator. If the pot is struck, the bomb will go off, so they counterfactual 'if the pot were struck it would break' is true, but it is not a fragile pot. This is a 'mimic' of the disposition. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 2.2.5.1) | |
| A reaction: A very nice example, showing that a true disposition would have to be an internal feature (a power) of the pot itself, not a mere disposition to behave. The problem is these pesky empiricists, who want to reduce it all to what is observable. |
| 9499 | Megarian actualists deny unmanifested dispositions [Bird] |
| Full Idea: The Megarian actualist denies that a disposition can exist without being manifested. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 5.4) | |
| A reaction: I agree with Bird that this extreme realism seems wrong. As he puts it (p.109), "unrealized possibilities must be part of the actual world". This commitment is beginning to change my understanding of the world I am looking at. |
| 9486 | Why should a universal's existence depend on instantiation in an existing particular? [Bird] |
| Full Idea: An instantiation condition seems to be a failure of nerve as regards realism about universals. If universals really are entities in their own right, why should their existence depend upon a relationship with existing particulars? | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.2.2) | |
| A reaction: I like this challenge, which seems to leave fans of universals no option but full-blown Platonism, which most of them recognise as being deeply implausible. |
| 9472 | Resemblance itself needs explanation, presumably in terms of something held in common [Bird] |
| Full Idea: The realist view of resemblance nominalism is that it is resemblance that needs explaining. When there is resemblance it is natural to want to explain it, in terms of something held in common. Explanations end somewhere, but not with resemblance. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 2.1.2) | |
| A reaction: I smell a regress. If a knife and a razor resemble because they share sharpness, you have to see that the sharp phenomenon falls within the category of 'sharpness' before you can make the connection, which is spotting its similarity. |
| 9482 | If the laws necessarily imply p, that doesn't give a new 'nomological' necessity [Bird] |
| Full Idea: It does not add to the kinds of necessity to say that p is 'nomologically necessary' iff (the laws of nature → p) is metaphysically necessary. That trick of construction could be pulled for 'feline necessity' (true in all worlds that contain cats). | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.1.2) | |
| A reaction: I love it! Bird seems to think that the only necessity is 'metaphysical' necessity, true in all possible worlds, and he is right. The question arises in modal logic, though, of the accessibility between worlds (which might give degrees of necessity?). |
| 9481 | Logical necessitation is not a kind of necessity; George Orwell not being Eric Blair is not a real possibility [Bird] |
| Full Idea: I do not regard logical necessitation as a kind of necessity. It is logically possible that George Orwell is not Eric Blair, but in what sense is this any kind of possibility? It arises from having two names, but that confers no genuine possibility. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.1.2) | |
| A reaction: How refreshing. All kinds of concepts like this are just accepted by philosophers as obvious, until someone challenges them. The whole undergrowth of modal thinking needs a good flamethrower taken to it. |
| 9505 | Empiricist saw imaginability and possibility as close, but now they seem remote [Bird] |
| Full Idea: Whereas the link between imaginability and possibility was once held, under the influence of empiricism, to be close, it is now widely held to be very remote. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 8) | |
| A reaction: Tim Williamson nicely argues the opposite - that assessment of possibility is an adjunct of our ability to think counterfactually, which is precisely an operation of the imagination. Big error is possible, but how else could we do it? |
| 9491 | Haecceitism says identity is independent of qualities and without essence [Bird] |
| Full Idea: The core of haecceitism is the view that the transworld identity of particulars does not supervene on their qualitative features. ...The simplest expression of it is that particulars lack essential properties. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 4.2.1) | |
| A reaction: This seems to be something the 'bare substratum' account of substance (associated with Locke). You are left with the difficulty of how to individuate an instance of the haecceity, as opposed to the bundle of properties attached to it. |
| 9487 | We can't reject all explanations because of a regress; inexplicable A can still explain B [Bird] |
| Full Idea: Some regard the potential regress of explanations as a reason to think that the very idea of explanation is illusory. This is a fallacy; it is not a necessary condition on A's explaining B that we have an explanation for A also. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.2.4) | |
| A reaction: True, though to say 'B is explained by A, but A is totally baffling' is not the account we are dreaming of. And the explanation would certainly fail if we could say nothing at all about A, apart from naming it. |
| 10110 | Corresponding to every concept there is a class (some of them sets) [George/Velleman] |
| Full Idea: Corresponding to every concept there is a class (some classes will be sets, the others proper classes). | |
| From: A.George / D.J.Velleman (Philosophies of Mathematics [2002], Ch.4) |
| 19399 | Prime matter is nothing when it is at rest [Leibniz] |
| Full Idea: Primary matter is nothing if considered at rest. | |
| From: Gottfried Leibniz (Aristotle and Descartes on Matter [1671], p.90) | |
| A reaction: This goes with Leibniz's Idea 13393, that activity is the hallmark of existence. No one seems to have been able to make good sense of prime matter, and it plays little role in Aristotle's writings. |
| 9493 | We should explain causation by powers, not powers by causation [Bird] |
| Full Idea: The notion of 'causal power' is not to be analysed in terms of causation; if anything, the relationship is the reverse. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 4.2.1 n71) | |
| A reaction: It is a popular view these days to take causation as basic (as opposed to the counterfactual account), but I prefer this view. If anything is basic in nature, it is the dynamic force in the engine room, which is the active powers of substances. |
| 9494 | Singularism about causes is wrong, as the universals involved imply laws [Bird] |
| Full Idea: While singularists about causation might think that a particular has its causal powers independently of law, it is difficult to see how a universal could have or confer causal powers without generating what we would naturally think of as a law. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 4.2.1 n71) | |
| A reaction: This is a middle road between the purely singularist account (Anscombe) and the fully nomological account. We might say that a caused event will be 'involved in law-like behaviour', without attributing the cause to a law. |
| 9507 | Laws are explanatory relationships of things, which supervene on their essences [Bird] |
| Full Idea: The laws of a domain are the fundamental, general explanatory relationships between kinds, quantities, and qualities of that domain, that supervene upon the essential natures of those things. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 10.1) | |
| A reaction: This is the scientific essentialist view of laws [see entries there, in 'Laws of Nature']. There seems uncertainty between 'kinds' and 'qualities' (with 'quantities' looking like a category mistake). I vote, with Ellis, for natural kinds as the basis. |
| 9488 | Laws are either disposition regularities, or relations between properties [Bird] |
| Full Idea: Instead of viewing laws as regular relationships between dispositional properties and stimulus-manifestation, they can be conceived of as a relation between properties. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.4) | |
| A reaction: Bird offers these as the two main views, with the first coming from scientific essentialism, and the second from Armstrong's account of universals. Personally I favour the first, but Bird suggests that powers give the best support for both views. |
| 9496 | That other diamonds are hard does not explain why this one is [Bird] |
| Full Idea: The fact that some other diamonds are hard does not explain why this diamond is hard. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 4.3.2) | |
| A reaction: A very nice aphorism! It pinpoints the whole error of trying to explain the behaviour of the world by citing laws. Why should this item obey that law? Bird prefers 'powers', and so do I. |
| 9479 | Dispositional essentialism says laws (and laws about laws) are guaranteed regularities [Bird] |
| Full Idea: For the regularity version of dispositional essentialism about laws, laws are those regularities whose truth is guaranteed by the essential dispositional nature of one or more of the constituents. Regularities that supervene on such laws are also laws. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.1.2) | |
| A reaction: Even if you accept necessary behaviour resulting from essential dispositions, you still need to distinguish the important regularities from the accidental ones, so the word 'guarantee' is helpful, even if it raises lots of difficulties. |
| 9473 | Laws cannot offer unified explanations if they don't involve universals [Bird] |
| Full Idea: Laws, or what flow from them, are supposed to provide a unified explanation of the behaviours of particulars. Without universals the explanation of the behaviours of things lacks the required unity. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 2.1.2) | |
| A reaction: Sounds a bit question-begging? Gravity seems fairly unified, whereas the frequency of London buses doesn't. Maybe I could unify bus-behaviour by positing a few new universals? The unity should first be in the phenomena, not in the explanation. |
| 9484 | If the universals for laws must be instantiated, a vanishing particular could destroy a law [Bird] |
| Full Idea: If universals exist only where and when they are instantiated, this make serious trouble for the universals view of laws. It would be most odd if a particular, merely by changing its properties, could cause a law to go out of existence. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.2.2) | |
| A reaction: This sounds conclusive. He notes that this is probably why Armstrong does not adopt this view (though Lowe seems to favour it). Could there be a possible property (and concomitant law) which was never ever instantiated? |
| 9506 | Salt necessarily dissolves in water, because of the law which makes the existence of salt possible [Bird] |
| Full Idea: We cannot have a world where it is true both that salt exists (which requires Coulomb's Law to be true), and that it fails to dissolve in water (which requires Coulomb's Law to be false). So the dissolving is necessary even if the Law is contingent. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 8.2) | |
| A reaction: Excellent. It is just like the bonfire on the Moon (imaginable through ignorance, but impossible). People who assert that the solubility of salt is contingent tend not to know much about chemistry. |
| 23713 | Most laws supervene on fundamental laws, which are explained by basic powers [Bird, by Friend/Kimpton-Nye] |
| Full Idea: According to Bird, non-fundamental laws supervene on fundamental laws, and so are ultimately explained by fundamental powers. | |
| From: report of Alexander Bird (Nature's Metaphysics [2007]) by Friend/Kimpton-Nye - Dispositions and Powers 3.6.1 | |
| A reaction: This looks like the picture I subscribe to. Roughly, fundamental laws are explained by powers, and non-fundamental laws are explained by properties, which are complexes of powers. 'Fundamental' may not be a precise term! |
| 9489 | Essentialism can't use conditionals to explain regularities, because of possible interventions [Bird] |
| Full Idea: The straightforward dispositional essentialist account of laws by subjunctive conditionals is false because dispositions typically suffer from finks and antidotes. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 3.4) | |
| A reaction: [Finks and antidotes intervene before a disposition can take effect] This seems very persuasive to me, and shows why you can't just explain laws as counterfactual or conditional claims. Explanation demands what underlies them. |
| 9504 | The relational view of space-time doesn't cover times and places where things could be [Bird] |
| Full Idea: The obvious problem with the simple relational view of space and time is that it fails to account for the full range of spatio-temporal possibility. There seem to be times and places where objects and events could be, but are not. | |
| From: Alexander Bird (Nature's Metaphysics [2007], 7.3.2) | |
| A reaction: This view seems strongly supported by intuition. I certainly don't accept the views of physicists and cosmologists on the subject, because they seem to approach the whole thing too instrumentally. |