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. |
| 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) |
| 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. |
| 468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
| Full Idea: In singing and playing the lyre, a boy will be likely to reveal not only courage and moderation, but also justice. | |
| From: Damon (fragments/reports [c.460 BCE], B4), quoted by (who?) - where? |
| 22594 | In 1794 France all individual and legal rights were suppressed by the general will [Dunt] |
| Full Idea: In the French Revolution the general will replaced democracy, the separation of powers, the rule of law, and individual rights. | |
| From: Ian Dunt (How to be a Liberal [2020], 03) | |
| A reaction: I had some sympathy with the idea of the general will, but Dunt has persuaded me otherwise. It is the embodiment of the democratic problem of the tyranny of the majority. |
| 22602 | Over several centuries a set of eight main liberal values was established [Dunt] |
| Full Idea: Over the centuries liberal values were established: freedom of the individual, reason, consent in government, individual rights, the separation of powers, protection of minorities, autonomy, and moderation. | |
| From: Ian Dunt (How to be a Liberal [2020], 13) | |
| A reaction: What's not to like? 'Moderation' might be a sticking point, for anyone who thinks that very large social changes are needed. |
| 22596 | No government, or the whole nation, can control an individual beyond legitimate scope [Dunt] |
| Full Idea: When a government of any sort puts a threatening hand on that part of individual life beyond its proper scope, …even if it were the whole nation, except for the man it is harassing, it would be no more legitimate for that. | |
| From: Ian Dunt (How to be a Liberal [2020]), quoted by Ian Dunt - How to be a Liberal 4 | |
| A reaction: The obvious question is what counts as 'proper scope' - and who gets to define it? If the individual can define that, then criminals can appeal to this principle. The state must be persuaded of it, then asked to stick to it during conflicts. |
| 22603 | Laissez-faire liberalism failed to give people the protections and freedoms needed for a good life [Dunt] |
| Full Idea: Laissez-faire liberalism failed, because it did not offer people protections and real freedom - against discrimination, insecure work, educational disadvantage, lack of social respect, absence of representation. It was cold, distant, and ineffective. | |
| From: Ian Dunt (How to be a Liberal [2020], 13) | |
| A reaction: A very nice summary, which I take to be correct. |
| 22592 | Nationalism pretends that we can only have a single identity [Dunt] |
| Full Idea: Nationalism pretends that there is only one identity, that we cannot be more than one thing at once. | |
| From: Ian Dunt (How to be a Liberal [2020], Today) | |
| A reaction: Dunt is a defender of liberalism, which assumes a wide degree of pluralism. Could I be a British citizen, but love France more than Britain? I don’t see why not, but it is not an ideal situation. |