21 ideas
| 14239 | The empty set is usually derived from Separation, but it also seems to need Infinity [Oliver/Smiley] |
| Full Idea: The empty set is usually derived via Zermelo's axiom of separation. But the axiom of separation is conditional: it requires the existence of a set in order to generate others as subsets of it. The original set has to come from the axiom of infinity. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 1.2) | |
| A reaction: They charge that this leads to circularity, as Infinity depends on the empty set. |
| 14240 | The empty set is something, not nothing! [Oliver/Smiley] |
| Full Idea: Some authors need to be told loud and clear: if there is an empty set, it is something, not nothing. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 1.2) | |
| A reaction: I'm inclined to think of a null set as a pair of brackets, so maybe that puts it into a metalanguage. |
| 14241 | We don't need the empty set to express non-existence, as there are other ways to do that [Oliver/Smiley] |
| Full Idea: The empty set is said to be useful to express non-existence, but saying 'there are no Us', or ¬∃xUx are no less concise, and certainly less roundabout. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 1.2) |
| 14242 | Maybe we can treat the empty set symbol as just meaning an empty term [Oliver/Smiley] |
| Full Idea: Suppose we introduce Ω not as a term standing for a supposed empty set, but as a paradigm of an empty term, not standing for anything. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 1.2) | |
| A reaction: This proposal, which they go on to explore, seems to mean that Ω (i.e. the traditional empty set symbol) is no longer part of set theory but is part of semantics. |
| 14243 | The unit set may be needed to express intersections that leave a single member [Oliver/Smiley] |
| Full Idea: Thomason says with no unit sets we couldn't call {1,2}∩{2,3} a set - but so what? Why shouldn't the intersection be the number 2? However, we then have to distinguish three different cases of intersection (common subset or member, or disjoint). | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 2.2) |
| 14234 | If you only refer to objects one at a time, you need sets in order to refer to a plurality [Oliver/Smiley] |
| Full Idea: A 'singularist', who refers to objects one at a time, must resort to the language of sets in order to replace plural reference to members ('Henry VIII's wives') by singular reference to a set ('the set of Henry VIII's wives'). | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], Intro) | |
| A reaction: A simple and illuminating point about the motivation for plural reference. Null sets and singletons give me the creeps, so I would personally prefer to avoid set theory when dealing with ontology. |
| 14237 | We can use plural language to refer to the set theory domain, to avoid calling it a 'set' [Oliver/Smiley] |
| Full Idea: Plurals earn their keep in set theory, to answer Skolem's remark that 'in order to treat of 'sets', we must begin with 'domains' that are constituted in a certain way'. We can speak in the plural of 'the objects', not a 'domain' of objects. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], Intro) | |
| A reaction: [Skolem 1922:291 in van Heijenoort] Zermelo has said that the domain cannot be a set, because every set belongs to it. |
| 14245 | Logical truths are true no matter what exists - but predicate calculus insists that something exists [Oliver/Smiley] |
| Full Idea: Logical truths should be true no matter what exists, so true even if nothing exists. The classical predicate calculus, however, makes it logically true that something exists. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 5.1) |
| 14246 | If mathematics purely concerned mathematical objects, there would be no applied mathematics [Oliver/Smiley] |
| Full Idea: If mathematics was purely concerned with mathematical objects, there would be no room for applied mathematics. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 5.1) | |
| A reaction: Love it! Of course, they are using 'objects' in the rather Fregean sense of genuine abstract entities. I don't see why fictionalism shouldn't allow maths to be wholly 'pure', although we have invented fictions which actually have application. |
| 14247 | Sets might either represent the numbers, or be the numbers, or replace the numbers [Oliver/Smiley] |
| Full Idea: Identifying numbers with sets may mean one of three quite different things: 1) the sets represent the numbers, or ii) they are the numbers, or iii) they replace the numbers. | |
| From: Oliver,A/Smiley,T (What are Sets and What are they For? [2006], 5.2) | |
| A reaction: Option one sounds the most plausible to me. I will take numbers to be patterns embedded in nature, and sets are one way of presenting them in shorthand form, in order to bring out what is repeated. |
| 16062 | A necessary relation between fact-levels seems to be a further irreducible fact [Lynch/Glasgow] |
| Full Idea: It seems unavoidable that the facts about logically necessary relations between levels of facts are themselves logically distinct further facts, irreducible to the microphysical facts. | |
| From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], C) | |
| A reaction: I'm beginning to think that rejecting every theory of reality that is proposed by carefully exposing some infinite regress hidden in it is a rather lazy way to do philosophy. Almost as bad as rejecting anything if it can't be defined. |
| 16061 | If some facts 'logically supervene' on some others, they just redescribe them, adding nothing [Lynch/Glasgow] |
| Full Idea: Logical supervenience, restricted to individuals, seems to imply strong reduction. It is said that where the B-facts logically supervene on the A-facts, the B-facts simply re-describe what the A-facts describe, and the B-facts come along 'for free'. | |
| From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], C) | |
| A reaction: This seems to be taking 'logically' to mean 'analytically'. Presumably an entailment is logically supervenient on its premisses, and may therefore be very revealing, even if some people think such things are analytic. |
| 16060 | Nonreductive materialism says upper 'levels' depend on lower, but don't 'reduce' [Lynch/Glasgow] |
| Full Idea: The root intuition behind nonreductive materialism is that reality is composed of ontologically distinct layers or levels. …The upper levels depend on the physical without reducing to it. | |
| From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], B) | |
| A reaction: A nice clear statement of a view which I take to be false. This relationship is the sort of thing that drives people fishing for an account of it to use the word 'supervenience', which just says two things seem to hang out together. Fluffy materialism. |
| 16064 | The hallmark of physicalism is that each causal power has a base causal power under it [Lynch/Glasgow] |
| Full Idea: Jessica Wilson (1999) says what makes physicalist accounts different from emergentism etc. is that each individual causal power associated with a supervenient property is numerically identical with a causal power associated with its base property. | |
| From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], n 11) | |
| A reaction: Hence the key thought in so-called (serious, rather than self-evident) 'emergentism' is so-called 'downward causation', which I take to be an idle daydream. |
| 8122 | True works of art transmit completely new feelings [Tolstoy] |
| Full Idea: Only that is a true work of art which transmits fresh feelings not previously experienced by man. | |
| From: Leo Tolstoy (What is Art? [1898], Ch.9) | |
| A reaction: I think a great composer will probably not have any new feelings at all, but will discover new expressions which contain feelings by which even they are surprised (e.g. the Tristan chord). |
| 8121 | Art is when one man uses external signs to hand on his feelings to another man [Tolstoy] |
| Full Idea: Art is a human activity in which one man consciously by means of external signs, hands on to others feelings he has lived through, and other are infected by those feelings, and also experience them. | |
| From: Leo Tolstoy (What is Art? [1898], Ch.5) | |
| A reaction: Such definitions always work better for some art forms than for others. This may fit 'Anna Karenin' quite well, but probably not Bach's 'Art of Fugue'. Writing obscenities on someone's front door would fit this definition. |
| 8124 | The highest feelings of mankind can only be transmitted by art [Tolstoy] |
| Full Idea: The highest feelings to which mankind has attained can only be transmitted from man to man by art. | |
| From: Leo Tolstoy (What is Art? [1898], Ch.17) | |
| A reaction: We are much more nervous these days of talking about 'highest' feelings. Tolstoy obviously considers religion to be an ingredient of the highest feelings, but that prevents us from judging them purely as feelings. Music is the place to rank feelings. |
| 8123 | The purpose of art is to help mankind to evolve better, more socially beneficial feelings [Tolstoy] |
| Full Idea: The evolution of feeling proceeds by means of art - feelings less kind and less necessary for the well-being of mankind being replaced by others kinder and more needful for that end. That is the purpose of art. | |
| From: Leo Tolstoy (What is Art? [1898], Ch.16) | |
| A reaction: Underneath his superficially expressivist view of art, Tolstoy is really an old-fashioned moralist about it, like Dr Johnson. This is the moralism of the great age of the nineteenth century novel (which was, er, the greatest age of the novel!). |
| 22710 | People estimate art according to their moral values [Tolstoy] |
| Full Idea: The estimation of the value of art …depends on men's perception of the meaning of life; depends on what they hold to be the good and evil of life. | |
| From: Leo Tolstoy (What is Art? [1898]), quoted by Iris Murdoch - The Sublime and the Good p.206 | |
| A reaction: [No ref given] This is put to the test by the insightful depiction of wickedness. We condemn the wickedness and admire the insight. Every reading of a novel is a moral journey, though I'm not sure how the true psychopath reads a novel. |
| 8125 | The upper classes put beauty first, and thus freed themselves from morality [Tolstoy] |
| Full Idea: The people of the upper class, more and more frequently encountering the contradictions between beauty and goodness, put the ideal of beauty first, thus freeing themselves from the demands of morality. | |
| From: Leo Tolstoy (What is Art? [1898], Ch.17) | |
| A reaction: The rich are a great deal freer to pursue the demands of beauty than are the poor. They also have a tradition of 'immorality' (such as duels and adultery) which was in place long before they discovered art. |
| 8064 | We separate the concept of beauty from goodness, unlike the ancients [Tolstoy] |
| Full Idea: The ancients had not that conception of beauty separated from goodness which forms the basis and aim of aesthetics in our time. | |
| From: Leo Tolstoy (What is Art? [1898], Ch.3) | |
| A reaction: This is written at around the time of the Aesthetic Movement, but Tolstoy's own novels are intensely moral. This separation makes abstract painting possible. |