17 ideas
| 10807 | Mathematics reduces to set theory, which reduces, with some mereology, to the singleton function [Lewis] |
| Full Idea: It is generally accepted that mathematics reduces to set theory, and I argue that set theory in turn reduces, with some aid of mereology, to the theory of the singleton function. | |
| From: David Lewis (Mathematics is Megethology [1993], p.03) |
| 10809 | We can accept the null set, but not a null class, a class lacking members [Lewis] |
| Full Idea: In my usage of 'class', there is no such things as the null class. I don't mind calling some memberless thing - some individual - the null set. But that doesn't make it a memberless class. Rather, that makes it a 'set' that is not a class. | |
| From: David Lewis (Mathematics is Megethology [1993], p.05) | |
| A reaction: Lewis calls this usage 'idiosyncratic', but it strikes me as excellent. Set theorists can have their vital null class, and sensible people can be left to say, with Lewis, that classes of things must have members. |
| 10811 | The null set plays the role of last resort, for class abstracts and for existence [Lewis] |
| Full Idea: The null set serves two useful purposes. It is a denotation of last resort for class abstracts that denote no nonempty class. And it is an individual of last resort: we can count on its existence, and fearlessly build the hierarchy of sets from it. | |
| From: David Lewis (Mathematics is Megethology [1993], p.09) | |
| A reaction: This passage assuages my major reservation about the existence of the null set, but at the expense of confirming that it must be taken as an entirely fictional entity. |
| 10812 | The null set is not a little speck of sheer nothingness, a black hole in Reality [Lewis] |
| Full Idea: Should we accept the null set as a most extraordinary individual, a little speck of sheer nothingness, a sort of black hole in the fabric of Reality itself? Not that either, I think. | |
| From: David Lewis (Mathematics is Megethology [1993], p.09) | |
| A reaction: Correct! |
| 10813 | What on earth is the relationship between a singleton and an element? [Lewis] |
| Full Idea: A new student of set theory has just one thing, the element, and he has another single thing, the singleton, and not the slightest guidance about what one thing has to do with the other. | |
| From: David Lewis (Mathematics is Megethology [1993], p.12) |
| 10814 | Are all singletons exact intrinsic duplicates? [Lewis] |
| Full Idea: Are all singletons exact intrinsic duplicates? | |
| From: David Lewis (Mathematics is Megethology [1993], p.13) |
| 10806 | Megethology is the result of adding plural quantification to mereology [Lewis] |
| Full Idea: Megethology is the result of adding plural quantification, as advocated by George Boolos, to the language of mereology. | |
| From: David Lewis (Mathematics is Megethology [1993], p.03) |
| 10816 | We can use mereology to simulate quantification over relations [Lewis] |
| Full Idea: We can simulate quantification over relations using megethology. Roughly, a quantifier over relations is a plural quantifier over things that encode ordered pairs by mereological means. | |
| From: David Lewis (Mathematics is Megethology [1993], p.18) | |
| A reaction: [He credits this idea to Burgess and Haven] The point is to avoid second-order logic, which quantifies over relations as ordered n-tuple sets. |
| 10245 | One geometry cannot be more true than another [Poincaré] |
| Full Idea: One geometry cannot be more true than another; it can only be more convenient. | |
| From: Henri Poincaré (Science and Method [1908], p.65), quoted by Stewart Shapiro - Philosophy of Mathematics | |
| A reaction: This is the culminating view after new geometries were developed by tinkering with Euclid's parallels postulate. |
| 10808 | Mathematics is generalisations about singleton functions [Lewis] |
| Full Idea: We can take the theory of singleton functions, and hence set theory, and hence mathematics, to consist of generalisations about all singleton functions. | |
| From: David Lewis (Mathematics is Megethology [1993], p.03) | |
| A reaction: At first glance this sounds like a fancy version of the somewhat discredited Greek idea that mathematics is built on the concept of a 'unit'. |
| 10815 | We don't need 'abstract structures' to have structural truths about successor functions [Lewis] |
| Full Idea: We needn't believe in 'abstract structures' to have general structural truths about all successor functions. | |
| From: David Lewis (Mathematics is Megethology [1993], p.16) |
| 14330 | To be realists about dispositions, we can only discuss them through their categorical basis [Armstrong] |
| Full Idea: It is only to the extent that we relate disposition to 'categorical basis', and difference of disposition to difference of 'categorical basis', that we can speak of dispositions. We must be Realists, not Phenomenalists, about dispositions. | |
| From: David M. Armstrong (A Materialist Theory of Mind (Rev) [1968], 6.VI) | |
| A reaction: It is Armstrong's realism which motivates this claim, because he thinks only categorical properties are real. But categorical properties seem to be passive, and the world is active. |
| 10810 | I say that absolutely any things can have a mereological fusion [Lewis] |
| Full Idea: I accept the principle of Unrestricted Composition: whenever there are some things, no matter how many or how unrelated or how disparate in character they may be, they have a mereological fusion. ...The trout-turkey is part fish and part fowl. | |
| From: David Lewis (Mathematics is Megethology [1993], p.07) | |
| A reaction: This nicely ducks the question of when things form natural wholes and when they don't, but I would have thought that that might be one of the central issues of metaphysicals, so I think I'll give Lewis's principle a miss. |
| 6498 | Armstrong suggests secondary qualities are blurred primary qualities [Armstrong, by Robinson,H] |
| Full Idea: According to D.M. Armstrong and others, when we perceive secondary qualities we are in fact perceiving primary qualities in a confused, indistinct or blurred way. | |
| From: report of David M. Armstrong (A Materialist Theory of Mind (Rev) [1968], 270-90) by Howard Robinson - Perception III.1 | |
| A reaction: This is obviously an attempt to fit secondary qualities into a reductive physicalist account of the mind. Personally I favour Armstrong's project, but doubt whether this strategy is necessary. I just don't think there is anything 'primary' about redness. |
| 5690 | A mental state without belief refutes self-intimation; a belief with no state refutes infallibility [Armstrong, by Shoemaker] |
| Full Idea: For Armstrong, introspection involves a belief, and mental states and their accompanying beliefs are 'distinct existences', so a state without belief shows states are not self-intimating, and the belief without the state shows beliefs aren't infallible. | |
| From: report of David M. Armstrong (A Materialist Theory of Mind (Rev) [1968]) by Sydney Shoemaker - Introspection | |
| A reaction: I agree with Armstrong. Introspection is a two-level activity, which animals probably can't do, and there is always the possibility of a mismatch between the two levels, so introspection is neither self-intimating nor infallibe (though incorrigible). |
| 5493 | If pains are defined causally, and research shows that the causal role is physical, then pains are physical [Armstrong, by Lycan] |
| Full Idea: Armstrong and Lewis said that mental items were defined in terms of typical causes and effects; if, as seems likely, research reveals that a particular causal niche is occupied by a physical state, it follows that pain is a physical state. | |
| From: report of David M. Armstrong (A Materialist Theory of Mind (Rev) [1968]) by William Lycan - Introduction - Ontology p.5 | |
| A reaction: I am not fully convinced of the first step in the argument. It sounds like the epistemology and the ontology have got muddled (as usual). We define mental states as we define electrons, in terms of observed behaviour, but what are they? |
| 4600 | Armstrong and Lewis see functionalism as an identity of the function and its realiser [Armstrong, by Heil] |
| Full Idea: The Armstrong/Lewis version of functionalism takes mental properties to be functional properties, but identifies these with what other functionalists would regard as their realisers. | |
| From: report of David M. Armstrong (A Materialist Theory of Mind (Rev) [1968]) by John Heil - Philosophy of Mind Ch.4 | |
| A reaction: Heil rejects this, but I am beginning to think that this is the answer. If functions do not have an ontological life of their own (the 'ringing' of the bell), then functionalist mental states can't either. Function is not an ontological category. |