27 ideas
| 4036 | What matters is not how many entities we postulate, but how many kinds of entities [Armstrong, by Mellor/Oliver] |
| Full Idea: Armstrong argues that what matters is not how few entities we postulate (quantitative economy), but how few kinds of entities (qualitative economy). | |
| From: report of David M. Armstrong (Properties [1992]) by DH Mellor / A Oliver - Introduction to 'Properties' §9 | |
| A reaction: Is this what Ockham meant? Armstrong is claiming that the notion of a 'property' is needed to identify kinds. See also Idea 7038. |
| 10476 | The idea that groups of concepts could be 'implicitly defined' was abandoned [Hodges,W] |
| Full Idea: Late nineteenth century mathematicians said that, although plus, minus and 0 could not be precisely defined, they could be partially 'implicitly defined' as a group. This nonsense was rejected by Frege and others, as expressed in Russell 1903. | |
| From: Wilfrid Hodges (Model Theory [2005], 2) | |
| A reaction: [compressed] This is helpful in understanding what is going on in Frege's 'Grundlagen'. I won't challenge Hodges's claim that such definitions are nonsense, but there is a case for understanding groups of concepts together. |
| 10478 | Since first-order languages are complete, |= and |- have the same meaning [Hodges,W] |
| Full Idea: In first-order languages the completeness theorem tells us that T |= φ holds if and only if there is a proof of φ from T (T |- φ). Since the two symbols express the same relationship, theorist often just use |- (but only for first-order!). | |
| From: Wilfrid Hodges (Model Theory [2005], 3) | |
| A reaction: [actually no spaces in the symbols] If you are going to study this kind of theory of logic, the first thing you need to do is sort out these symbols, which isn't easy! |
| 10477 | |= in model-theory means 'logical consequence' - it holds in all models [Hodges,W] |
| Full Idea: If every structure which is a model of a set of sentences T is also a model of one of its sentences φ, then this is known as the model-theoretic consequence relation, and is written T |= φ. Not to be confused with |= meaning 'satisfies'. | |
| From: Wilfrid Hodges (Model Theory [2005], 3) | |
| A reaction: See also Idea 10474, which gives the other meaning of |=, as 'satisfies'. The symbol is ALSO used in propositional logical, to mean 'tautologically implies'! Sort your act out, logicians. |
| 10474 | |= should be read as 'is a model for' or 'satisfies' [Hodges,W] |
| Full Idea: The symbol in 'I |= S' reads that if the interpretation I (about word meaning) happens to make the sentence S state something true, then I 'is a model for' S, or I 'satisfies' S. | |
| From: Wilfrid Hodges (Model Theory [2005], 1) | |
| A reaction: Unfortunately this is not the only reading of the symbol |= [no space between | and =!], so care and familiarity are needed, but this is how to read it when dealing with models. See also Idea 10477. |
| 10481 | Models in model theory are structures, not sets of descriptions [Hodges,W] |
| Full Idea: The models in model-theory are structures, but there is also a common use of 'model' to mean a formal theory which describes and explains a phenomenon, or plans to build it. | |
| From: Wilfrid Hodges (Model Theory [2005], 5) | |
| A reaction: Hodges is not at all clear here, but the idea seems to be that model-theory offers a set of objects and rules, where the common usage offers a set of descriptions. Model-theory needs homomorphisms to connect models to things, |
| 10473 | Model theory studies formal or natural language-interpretation using set-theory [Hodges,W] |
| Full Idea: Model theory is the study of the interpretation of any language, formal or natural, by means of set-theoretic structures, with Tarski's truth definition as a paradigm. | |
| From: Wilfrid Hodges (Model Theory [2005], Intro) | |
| A reaction: My attention is caught by the fact that natural languages are included. Might we say that science is model theory for English? That sounds like Quine's persistent message. |
| 10475 | A 'structure' is an interpretation specifying objects and classes of quantification [Hodges,W] |
| Full Idea: A 'structure' in model theory is an interpretation which explains what objects some expressions refer to, and what classes some quantifiers range over. | |
| From: Wilfrid Hodges (Model Theory [2005], 1) | |
| A reaction: He cites as examples 'first-order structures' used in mathematical model theory, and 'Kripke structures' used in model theory for modal logic. A structure is also called a 'universe'. |
| 10480 | First-order logic can't discriminate between one infinite cardinal and another [Hodges,W] |
| Full Idea: First-order logic is hopeless for discriminating between one infinite cardinal and another. | |
| From: Wilfrid Hodges (Model Theory [2005], 4) | |
| A reaction: This seems rather significant, since mathematics largely relies on first-order logic for its metatheory. Personally I'm tempted to Ockham's Razor out all these super-infinities, but mathematicians seem to make use of them. |
| 15754 | Without properties we would be unable to express the laws of nature [Armstrong] |
| Full Idea: The ontological correlates of true law-statements must involve properties. How else can one pick our the uniformities which the law-statements entail? | |
| From: David M. Armstrong (Properties [1992], 1) | |
| A reaction: I'm unconvinced about the 'laws', but I have to admit that it is hard to know how to describe the relevant bits of nature without some family of concepts covered by the word 'property'. I'm in favour of taking some of the family into care, though. |
| 4034 | Whether we apply 'cold' or 'hot' to an object is quite separate from its change of temperature [Armstrong] |
| Full Idea: Evading properties by means of predicates is implausible when things change. If a cold thing becomes hot, first 'cold' applies, and then 'hot', but what have predicates to do with the temperature of an object? | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: A clear illustration of why properties are part of nature, not just part of language. But some applications of predicates are more arbitrary than this (ugly, cool) |
| 8535 | To the claim that every predicate has a property, start by eliminating failure of application of predicate [Armstrong] |
| Full Idea: Upholders of properties have been inclined to postulate a distinct property corresponding to each distinct predicate. We could start by eliminating all those properties where the predicate fails to apply, is not true, of anything. | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: This would leave billions of conjunctional, disjunctional and gerrymandered properties where the predicate applies very well. We are all 'on the same planet as New York'. Am I allowed to say that I 'wish' that a was F? He aims for 'sparse' properties. |
| 8537 | Tropes fall into classes, because exact similarity is symmetrical and transitive [Armstrong] |
| Full Idea: Exact similarity is a symmetrical and transitive relation. (Less than exact similarity is not transitive, even for tropes). So the relation of exact similarity is an equivalence relation, partitioning the field of tropes into equivalence classes. | |
| From: David M. Armstrong (Properties [1992], §2) | |
| A reaction: Armstrong goes on the explore the difficulties for trope theory of less than exact similarity, which is a very good line of discussion. Unfortunately it is a huge problem for everyone, apart from the austere nominalist. |
| 8538 | Trope theory needs extra commitments, to symmetry and non-transitivity, unless resemblance is exact [Armstrong] |
| Full Idea: Trope theory needs extra ontological baggage, the Axioms of Resemblance. There is a principle of symmetry, and there is the failure of transitivity - except in the special case of exact resemblance. | |
| From: David M. Armstrong (Properties [1992], §2) | |
| A reaction: [see text for fuller detail] Is it appropriate to describe such axioms as 'ontological' baggage? Interesting, though I suspect that any account of properties and predicates will have a similar baggage of commitments. |
| 8539 | Universals are required to give a satisfactory account of the laws of nature [Armstrong] |
| Full Idea: A reason why I reject trope theory is that universals are required to give a satisfactory account of the laws of nature. | |
| From: David M. Armstrong (Properties [1992], §2) | |
| A reaction: This is the key thought in Armstrong's defence of universals. Issues about universals may well be decided on such large playing fields. I think he is probably wrong, and I will gradually explain why. Watch this space as the story unfolds... |
| 8529 | Deniers of properties and relations rely on either predicates or on classes [Armstrong] |
| Full Idea: The great deniers of properties and relations are of two sorts: those who put their faith in predicates and those who appeal to sets (classes). | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: This ignores the Quine view, which is strictly for ostriches. Put like this, properties and relations seem undeniable. Predicates are too numerous (gerrymandering) or too few (colour shades). Classes can have arbitrary members. |
| 8532 | Resemblances must be in certain 'respects', and they seem awfully like properties [Armstrong] |
| Full Idea: If a resembles b, in general, they resemble in certain respects, and fail to resemble in other respects. But respects are uncomfortably close to properties, which the Resemblance theory proposes to do without. | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: This is a good objection. I think it is plausible to build a metaphysics around the idea of respects, and drop properties. Shall we just talk of 'respects' for categorising, and 'powers' for causation and explanation? Respects only exist in comparisons. |
| 8530 | Change of temperature in objects is quite independent of the predicates 'hot' and 'cold' [Armstrong] |
| Full Idea: To appreciate the implausibility of the predicate view, consider where a thing's properties change. 'Hot' becomes applicable when 'cold' ceases to, ..but the change in the object would have occurred if the predicates had never existed. | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: They keep involving secondary qualities! Armstrong is taking a strongly realist view (fine by me), but anti-realists can ignore his argument. I take predicate nominalism to be a non-starter. |
| 8536 | We want to know what constituents of objects are grounds for the application of predicates [Armstrong] |
| Full Idea: The properties that are of ontological interest are those constituents of objects, of particulars, which serve as the ground in the objects for the application of predicates. | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: Good. This is a reversal of the predicate nominalist approach, and is a much healthier attitude to the relationship between ontology and language. Value judgements will be an interesting case. Does this allow us to invent new predicates? |
| 8531 | In most sets there is no property common to all the members [Armstrong] |
| Full Idea: Most sets are uninteresting because they are utterly heterogeneous, that is, the members have nothing in common. For most sets there is no common property F, such that the set is the set of all the Fs. | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: One might link the interesting sets together by resemblance, without invoking the actual existence of an item F which all the members carry (like freemasons' briefcases). Personally I am only really interested in 'natural' sets. |
| 15753 | Essences might support Resemblance Nominalism, but they are too coarse and ill-defined [Armstrong] |
| Full Idea: A sophisticated Resemblance theory can appeal to the natures of the resembling things, from which the resemblances flow. The natures are suitably internal, but are as coarse as the things themselves (and perhaps are the things themselves). | |
| From: David M. Armstrong (Properties [1992], 1) | |
| A reaction: Note that this is essentialism as an underpinning for Resemblance Nominalism. His objection is that he just can't believe in essences, because they are too 'coarse' - which I take to mean that we cannot distinguish the boundaries of an essence. |
| 8533 | Predicates need ontological correlates to ensure that they apply [Armstrong] |
| Full Idea: Must there not be something quite specific about the thing which allows, indeed ensures, that predicates like 'underneath' and 'hot' apply? The predicates require ontological correlates. | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: An interesting proposal, that in addition to making use of predicates, we should 'ensure that they apply'. Sounds verificationist. Obvious problem cases would be speculative, controversial or metaphorical predicates. "He's beneath contempt". |
| 4035 | There must be some explanation of why certain predicates are applicable to certain objects [Armstrong] |
| Full Idea: When we have said that predicates apply to objects, we have surely not said enough. The situation cries out for an explanation. Must there not be something specific about the things which allows, indeed ensures, that these predicates apply? | |
| From: David M. Armstrong (Properties [1992], §1) | |
| A reaction: A nice challenge to any philosopher who places too much emphasis on language. A random and arbitrary (nominalist?) language simply wouldn't work. Nature has joints. |
| 1748 | Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius] |
| Full Idea: Archelaus was the first person to say that the universe is boundless. | |
| From: report of Archelaus (fragments/reports [c.450 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.Ar.3 |
| 8541 | Regularities theories are poor on causal connections, counterfactuals and probability [Armstrong] |
| Full Idea: Regularity theories make laws molecular, with no inner causal connections; also, only some cosmic regularities are manifestations of laws; molecular states can't sustain counterfactuals; and probabilistic laws are hard to accommodate. | |
| From: David M. Armstrong (Properties [1992], §2) | |
| A reaction: [very compressed] A helpful catalogue of difficulties. The first difficulty is the biggest one - that regularity theories have nothing to say about why there is a regularity. They offer descriptions instead of explanations. |
| 8540 | The introduction of sparse properties avoids the regularity theory's problem with 'grue' [Armstrong] |
| Full Idea: Regularity theories of laws face the grue problem. That, I think, can only be got over by introducing properties, sparse properties, into one's ontology. | |
| From: David M. Armstrong (Properties [1992], §2) | |
| A reaction: The problem is, roughly, that regularities have to be described in language, which is too arbitrary in character. Armstrong rightly tries to break the rigid link to language. See his Idea 8536, which puts reality before language. |
| 5989 | Archelaus said life began in a primeval slime [Archelaus, by Schofield] |
| Full Idea: Archelaus wrote that life on Earth began in a primeval slime. | |
| From: report of Archelaus (fragments/reports [c.450 BCE]) by Malcolm Schofield - Archelaus | |
| A reaction: This sounds like a fairly clearcut assertion of the production of life by evolution. Darwin's contribution was to propose the mechanism for achieving it. We should honour the name of Archelaus for this idea. |