56 ideas
19215 | Arguers often turn the opponent's modus ponens into their own modus tollens [Merricks] |
Full Idea: There is a seasoned method of turning your opponent's modus ponens into your own modus tollens. | |
From: Trenton Merricks (Propositions [2015], 5.VII) | |
A reaction: That is, they say 'if he's coming he'll be hear by now, and he's definitely coming', to which you say 'I'm afraid he's not here, so he obviously isn't coming after all'. They say if-A-then-B, and A, so B. You say not-B, so you're wrong about A. |
18405 | A 'teepee' argument has several mutually supporting planks to it [Cappelen/Dever] |
Full Idea: In a 'teepee' argument, a number of argumentative planks intersupport each other. No plank is sufficiently strong to establish the position, but each lends credibility to the others because there is the appearance of a unified phenomenon. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 01.5) | |
A reaction: To attack it, they say, you have to identify the separate planks of the argument. It is a moot point whether the teepee might be so imprecise that it is better described as 'coherence'. There is a background support, as well as the planks. |
19205 | 'Snow is white' only contingently expresses the proposition that snow is white [Merricks] |
Full Idea: It is contingently true that 'snow is white' expresses the proposition that snow is white. | |
From: Trenton Merricks (Propositions [2015], 1.V n14) | |
A reaction: Tarski stuck to sentences, but Merricks rightly argues that truth concerns propositions, not sentences. Sentences are subservient entities - mere tools used to express what matters, which is our thoughts (say I). |
19209 | Simple Quantified Modal Logc doesn't work, because the Converse Barcan is a theorem [Merricks] |
Full Idea: Logical consequence guarantees preservation of truth. The Converse Barcan, a theorem of Simple Quantified Modal Logic, says that an obvious truth implies an obvious falsehood. So SQML gets logical consequence wrong. So SQML is mistaken. | |
From: Trenton Merricks (Propositions [2015], 2.V) | |
A reaction: I admire this. The Converse Barcan certainly strikes me as wrong (Idea 19208). Merricks grasps this nettle. Williamson grasps the other nettle. Most people duck the issue, I suspect. Merricks says later that domains are the problem. |
19208 | The Converse Barcan implies 'everything exists necessarily' is a consequence of 'necessarily, everything exists' [Merricks] |
Full Idea: The Converse Barcan Formula has a startling result. Simple Quantified Modal Logic (SQML) has the following as a theorem: □∀xFx → ∀x□Fx. So 'everything exists necessarily' is a consequence of 'necessarily, everything exists'. | |
From: Trenton Merricks (Propositions [2015], 2.V) | |
A reaction: He says this is blatantly wrong. Williamson is famous for defending it. I think I'm with Merricks on this one. |
10859 | A set is 'well-ordered' if every subset has a first element [Clegg] |
Full Idea: For a set to be 'well-ordered' it is required that every subset of the set has a first element. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.13) |
10857 | Set theory made a closer study of infinity possible [Clegg] |
Full Idea: Set theory made a closer study of infinity possible. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.13) |
10864 | Any set can always generate a larger set - its powerset, of subsets [Clegg] |
Full Idea: The idea of the 'power set' means that it is always possible to generate a bigger one using only the elements of that set, namely the set of all its subsets. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.14) |
10872 | Extensionality: Two sets are equal if and only if they have the same elements [Clegg] |
Full Idea: Axiom of Extension: Two sets are equal if and only if they have the same elements. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) |
10875 | Pairing: For any two sets there exists a set to which they both belong [Clegg] |
Full Idea: Axiom of Pairing: For any two sets there exists a set to which they both belong. So you can make a set out of two other sets. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) |
10876 | Unions: There is a set of all the elements which belong to at least one set in a collection [Clegg] |
Full Idea: Axiom of Unions: For every collection of sets there exists a set that contains all the elements that belong to at least one of the sets in the collection. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) |
10878 | Infinity: There exists a set of the empty set and the successor of each element [Clegg] |
Full Idea: Axiom of Infinity: There exists a set containing the empty set and the successor of each of its elements. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) | |
A reaction: This is rather different from the other axioms because it contains the notion of 'successor', though that can be generated by an ordering procedure. |
10877 | Powers: All the subsets of a given set form their own new powerset [Clegg] |
Full Idea: Axiom of Powers: For each set there exists a collection of sets that contains amongst its elements all the subsets of the given set. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) | |
A reaction: Obviously this must include the whole of the base set (i.e. not just 'proper' subsets), otherwise the new set would just be a duplicate of the base set. |
10879 | Choice: For every set a mechanism will choose one member of any non-empty subset [Clegg] |
Full Idea: Axiom of Choice: For every set we can provide a mechanism for choosing one member of any non-empty subset of the set. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) | |
A reaction: This axiom is unusual because it makes the bold claim that such a 'mechanism' can always be found. Cohen showed that this axiom is separate. The tricky bit is choosing from an infinite subset. |
10871 | Axiom of Existence: there exists at least one set [Clegg] |
Full Idea: Axiom of Existence: there exists at least one set. This may be the empty set, but you need to start with something. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) |
10874 | Specification: a condition applied to a set will always produce a new set [Clegg] |
Full Idea: Axiom of Specification: For every set and every condition, there corresponds a set whose elements are exactly the same as those elements of the original set for which the condition is true. So the concept 'number is even' produces a set from the integers. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) | |
A reaction: What if the condition won't apply to the set? 'Number is even' presumably won't produce a set if it is applied to a set of non-numbers. |
19207 | Sentence logic maps truth values; predicate logic maps objects and sets [Merricks] |
Full Idea: The models for sentential logic map sentences to truth-values. The models for predicate logic map parts of sentences to objects and sets. | |
From: Trenton Merricks (Propositions [2015], 2.II) | |
A reaction: Logic books rarely tell you important things like this. That is why this database is so incredibly important! You will never understand the subject if you don't collect together the illuminating asides of discussion. They say it all so much more simply. |
10880 | Mathematics can be 'pure' (unapplied), 'real' (physically grounded); or 'applied' (just applicable) [Clegg] |
Full Idea: Three views of mathematics: 'pure' mathematics, where it doesn't matter if it could ever have any application; 'real' mathematics, where every concept must be physically grounded; and 'applied' mathematics, using the non-real if the results are real. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.17) | |
A reaction: Very helpful. No one can deny the activities of 'pure' mathematics, but I think it is undeniable that the origins of the subject are 'real' (rather than platonic). We do economics by pretending there are concepts like the 'average family'. |
10861 | Beyond infinity cardinals and ordinals can come apart [Clegg] |
Full Idea: With ordinary finite numbers ordinals and cardinals are in effect the same, but beyond infinity it is possible for two sets to have the same cardinality but different ordinals. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.13) |
10860 | An ordinal number is defined by the set that comes before it [Clegg] |
Full Idea: You can think of an ordinal number as being defined by the set that comes before it, so, in the non-negative integers, ordinal 5 is defined as {0, 1, 2, 3, 4}. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.13) |
10854 | Transcendental numbers can't be fitted to finite equations [Clegg] |
Full Idea: The 'transcendental numbers' are those irrationals that can't be fitted to a suitable finite equation, of which π is far and away the best known. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch. 6) |
10858 | By adding an axis of imaginary numbers, we get the useful 'number plane' instead of number line [Clegg] |
Full Idea: The realisation that brought 'i' into the toolkit of physicists and engineers was that you could extend the 'number line' into a new dimension, with an imaginary number axis at right angles to it. ...We now have a 'number plane'. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.12) |
10853 | Either lack of zero made early mathematics geometrical, or the geometrical approach made zero meaningless [Clegg] |
Full Idea: It is a chicken-and-egg problem, whether the lack of zero forced forced classical mathematicians to rely mostly on a geometric approach to mathematics, or the geometric approach made 0 a meaningless concept, but the two remain strongly tied together. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch. 6) |
10866 | Cantor's account of infinities has the shaky foundation of irrational numbers [Clegg] |
Full Idea: As far as Kronecker was concerned, Cantor had built a whole structure on the irrational numbers, and so that structure had no foundation at all. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) |
10869 | The Continuum Hypothesis is independent of the axioms of set theory [Clegg] |
Full Idea: Paul Cohen showed that the Continuum Hypothesis is independent of the axioms of set theory. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.15) |
10862 | The 'continuum hypothesis' says aleph-one is the cardinality of the reals [Clegg] |
Full Idea: The 'continuum hypothesis' says that aleph-one is the cardinality of the rational and irrational numbers. | |
From: Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch.14) |
19214 | In twinning, one person has the same origin as another person [Merricks] |
Full Idea: Origin essentialists claim that parental union results in a person, and that person could not have resulted from any other union. However, if the fertilised egg undergoes twinning, at least one of the resultant persons is not the original person. | |
From: Trenton Merricks (Propositions [2015], 5.V) | |
A reaction: Merricks says that therefore that origin could have just produced the second twin, rather than the original person. This is interesting, but doesn't seem to threaten the necessity of origin thesis. Once I'm here, I have that origin, despite my twin. |
18422 | Prioprioception focuses on your body parts, not on your self, or indexicality [Cappelen/Dever] |
Full Idea: Proprioception is not focused single-mindedly on the self, but is focused on a number of objects - the component bodily parts that belong to the self. There is no obvious need for a concept of the self, or of indexicality. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 07.2) |
18425 | We can acquire self-knowledge with mirrors, not just with proprioception and introspection [Cappelen/Dever] |
Full Idea: Imagine a being that learns everything about itself by watching itself in mirrors, rather than by proprioception and introspection. Surely it can get wet in a storm, even though allegedly distinctive routes of self-knowledge are not available to it? | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 09.3) | |
A reaction: [compressed] |
18421 | Proprioception is only immune from error if you are certain that it represents the agent [Cappelen/Dever] |
Full Idea: The guarantee of immunity from error in prioprioception is only as strong as the guarantee that proprioception only ever represents the proprioceiving agent. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 07.1) | |
A reaction: This is part of an interesting and sustained attack on the idea that self-knowledge is immune from error. They are thinking of science-fictiony situations where I am wired up to experience your leg movement. My experiences usually track me, that's all. |
18419 | Folk Functionalism is a Ramsification of our folk psychology [Cappelen/Dever] |
Full Idea: According to Folk Functionalism, mental states are theoretically defined by Ramsifying on our folk-psychological theory. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 06.2) |
18404 | It is assumed that indexical content is needed to represent the perspective of perception [Cappelen/Dever] |
Full Idea: Because our perceptual states typically represent the world as seen from a perspective, it is sometimes thought that some distinctively indexical kind of content is needed to characterise those states. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 01.4) | |
A reaction: They are summarising this view precisely so that they can oppose it, and I think they are right. |
18426 | All information is objective, and purely indexical information is not much use [Cappelen/Dever] |
Full Idea: Fundamentally, all information is objective information. ...[176] What we want is fully portable information, and information that co-ordinates on the world, rather than on us, is best suited for the task. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 10) | |
A reaction: I agree entirely with their thesis. We just pick up information about ourselves, such as who and where we are, which is just like equivalent information about other people. It is isn't a special type of information. |
18427 | If some of our thought is tied to its context, it will be hard to communicate it [Cappelen/Dever] |
Full Idea: It is bad news if some of our contents are essentially tied to particular contexts. ...If information needs to be assessed relative to some ur-context, later recipients won't know what to do with it. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 10) |
18428 | You don't remember your house interior just from an experienced viewpoint [Cappelen/Dever] |
Full Idea: When you recall the look of the inside of your house ....where things are relative to one another is what persists in memory, not where they were relative to you when seen. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 10) | |
A reaction: This seems to be a very telling example, though you could postulate some system which converts perspectival input into objective information. But why bother? We seek objective information, not perspectives. |
18429 | Our beliefs and desires are not organised around ourselves, but around the world [Cappelen/Dever] |
Full Idea: Our view on the world is not primarily a view from a perspective. Our beliefs and desires are not organized around us. They are instead organized around the world itself. Our view is a view from everywhere. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 10) | |
A reaction: Slipping in the claim that our desires are also organised around the world is not quite as persuasive as the claim about beliefs. If you want to draw a freehand straight line, focus on the far end of it. The world will guide your hand. |
18407 | Indexicality is not significantly connected to agency [Cappelen/Dever] |
Full Idea: There are no interesting or distinctive explanatory connections between indexicality and agency. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 01.8) |
19217 | I don't accept that if a proposition is directly about an entity, it has a relation to the entity [Merricks] |
Full Idea: The Aboutness Assumption says that necessarily, if a proposition is directly about an entity, then that proposition stands in a relation to the entity. I shall argue that the Assumption is false. | |
From: Trenton Merricks (Propositions [2015], 5.VII) | |
A reaction: This feels sort of right, though the nature of aboutness remains elusive. He cites denials of existence. I take speech to be fairly internal, even though its main role is communication. Maybe its a Cambridge relation, as far as the entity is concerned. |
19203 | A sentence's truth conditions depend on context [Merricks] |
Full Idea: A sentence has truth conditions only in a context of use. And the truth conditions of many sentences can differ from one context of use to another (as in 'I am a philosopher'). | |
From: Trenton Merricks (Propositions [2015], 1.II) | |
A reaction: He is building a defence of propositions, because they are eternal, and have their truth conditions essentially. I too am a fan of propositions. |
18413 | Fregeans can't agree on what 'senses' are [Cappelen/Dever] |
Full Idea: There is little agreement among Fregeans about what senses are. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 04.5) | |
A reaction: I don't take this to be sufficient grounds for dismissing Fregean senses. When we look into the workings of the linguistic mind, there seems little prospect of clarity or agreement. |
18417 | Possible worlds accounts of content are notoriously coarse-grained [Cappelen/Dever] |
Full Idea: Possible worlds accounts of content are notoriously coarse-grained. They fail to distinguish between logical or mathematical truths, ..between metaphysical equivalences, ..between coreferentials, ..and between indexicals and non-indexicals. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 05.5) | |
A reaction: [A nice summary, very compressed] |
18408 | Indexicals are just non-constant in meaning, and don't involve any special concepts [Cappelen/Dever] |
Full Idea: Once the non-constant characters of expressions has been characterised, there is no further need for additional devices like 'first-person concepts' or 'demonstrative concepts'. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 01.7) | |
A reaction: This seems to me to be a wonderfully liberating attack on this issue. There is a kind of creepy mysticism that has been allowed to accrue around indexicals, and it's nonsense. |
18414 | Fregeans say 'I' differs in reference, so it must also differ in sense [Cappelen/Dever] |
Full Idea: Fregeans tend to treat as a fundamental tenet that sense determines reference; same sense, same reference. From that it follow trivially that indexicals don't have the same sense: different uses of 'I' have different referents, so sense must differ. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 04.6) | |
A reaction: Interesting. Since it seems implausible that 'I' is profoundly different when two people use it, this seems to be a strong argument against Frege's distinction. But I rather like Frege's distinction, while being sceptical about 'I', so I'm baffled.... |
18423 | All indexicals can be expressed non-indexically [Cappelen/Dever] |
Full Idea: Whatever can be expressed indexically could be expressed by non-indexical means. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 08.1) | |
A reaction: This is the best summary of the thesis of their book. Indexicality in non-essential. |
19200 | Propositions are standardly treated as possible worlds, or as structured [Merricks] |
Full Idea: The thesis that propositions are sets of possible worlds is one of the two leading accounts of the nature of propositions. The other leading account endorses structured propositions. | |
From: Trenton Merricks (Propositions [2015], Intro) | |
A reaction: Merricks sets out to reject both main views. I take the idea that propositions actually are sets of possible worlds to be ridiculous (though they may offer a way of modelling them). The idea that they have no structure at all strikes me as odd. |
19206 | 'Cicero is an orator' represents the same situation as 'Tully is an orator', so they are one proposition [Merricks] |
Full Idea: The proposition expressed by 'Cicero is an orator' represents things as being exactly the same way as does the proposition expressed by 'Tully is an orator'. Hence two sentences express the same proposition. Fregeans about names deny this. | |
From: Trenton Merricks (Propositions [2015], 2.II) | |
A reaction: Merricks makes the situation in the world fix the contents of the proposition. I don't agree. I would expand the first proposition as 'The person I know as 'Cicero' was an orator', but I might never have heard of 'Tully'. |
19202 | Propositions are necessary existents which essentially (but inexplicably) represent things [Merricks] |
Full Idea: My account says that each proposition is a necessary existent that essentially represents things as being a certain way, ...and there is no explanation of how propositions do that. | |
From: Trenton Merricks (Propositions [2015], Intro) | |
A reaction: Since I take propositions to be brain events, I don't expect much of an explanation either. The idea that propositions necessarily exist strikes me as false. If there were no minds, there would have been no propositions. |
19204 | True propositions existed prior to their being thought, and might never be thought [Merricks] |
Full Idea: 1,000 years ago, no sentence had ever expressed, and no one had believed, the true proposition 'a water molecule has two hydrogen and one oxygen atoms'. There are surely true propositions that have never been, and never will be, expressed or believed. | |
From: Trenton Merricks (Propositions [2015], 1.V) | |
A reaction: 'Surely'? Surely not! How many propositions exist? Where do they exist? What are they made of? If they already exist when we think them, how do we tune into them? When did his example come into existence? Before water did? No! No! |
19210 | The standard view of propositions says they never change their truth-value [Merricks] |
Full Idea: The standard view among philosophers nowadays seems to be that propositions do not and even cannot change in truth-value. But my own view is that some propositions can, and do, change in truth value. | |
From: Trenton Merricks (Propositions [2015], 3.VII) | |
A reaction: He gives 'that A sits' as an example of one which can change, though 'that A sits at time t' cannot change. I take Merricks to be obviously right, and cannot get my head round the 'standard' view. What on earth do they think a proposition is? |
19201 | Propositions can be 'about' an entity, but that doesn't make the entity a constituent of it [Merricks] |
Full Idea: If a singular proposition is 'directly about' an entity, I argue that a singular proposition does not have the entity that it is directly about as a constituent. | |
From: Trenton Merricks (Propositions [2015], Intro) | |
A reaction: This opposes the view of the early Russell, that propositions actually contain the entities they are about, thus making propositions real features of the external world. I take that view of Russell's to be absurd. |
19211 | Early Russell says a proposition is identical with its truthmaking state of affairs [Merricks] |
Full Idea: I describe Russell's 1903 account of propositions as the view that each proposition is identical with the state of affairs that makes that proposition true. That is, a proposition is identical with its 'truthmaking' state of affairs. | |
From: Trenton Merricks (Propositions [2015], 4.II) | |
A reaction: Russell soon gave this view up (false propositions proving tricky), and I'm amazed anyone takes it seriously. I take it as axiomatic that if there were no minds there would be no propositions. Was the Big Bang a set of propositions? |
19212 | Unity of the proposition questions: what unites them? can the same constituents make different ones? [Merricks] |
Full Idea: What binds the constituents of a structured proposition together into a single unity, a proposition? Can the very same constituents constitute two distinct propositions? These are questions about 'the unity of the proposition'. | |
From: Trenton Merricks (Propositions [2015], 4.II) | |
A reaction: Merricks solves it by saying propositions have no structure. The problem is connected to the nature of predication (instantiation, partaking). You can't just list objects and their properties. Objects are united, and thus propositions are too. |
19213 | We want to explain not just what unites the constituents, but what unites them into a proposition [Merricks] |
Full Idea: A successful account of the unity of the proposition tells us what unites the relevant constituents not merely into some entity or other, but into a proposition. | |
From: Trenton Merricks (Propositions [2015], 4.X) | |
A reaction: Merrickes takes propositions to be unanalysable unities, but their central activity is representation, so if they needed uniting, that would be the place to look. Some people say that we unite our propositions. Others say the world does. I dunno. |
18406 | The basic Kaplan view is that there is truth-conditional content, and contextual character [Cappelen/Dever] |
Full Idea: In what we label 'Basic Kaplanianism', each of the sentences 'Smith is happy' and 'I am happy', as uttered by Smith, has two levels of meaning. The 'content' is a truth-conditional representation. The 'character' is a function from contexts to contents. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 01.6) | |
A reaction: They give this as a minimal and plausible account of the situation, without reading huge significance into the indexical. I'm inclined to see the situation in terms of the underlying proposition containing both ingredients. |
18411 | It is proposed that a huge range of linguistic items are context-sensitive [Cappelen/Dever] |
Full Idea: An enormous amount has been written about whether 'all', 'know', 'might', 'delicious', 'good', 'if, then', 'and', 'red', 'just', 'justified', 'probable', 'local', 'ready', and 'left-right' are context-sensitive. | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 02.3) | |
A reaction: The clearest way to approach these things is ask what the (informal) domain of quantification is for that particular context. The domain can shift in the course of a sentence. |
18420 | We deny that action involves some special class of beliefs [Cappelen/Dever] |
Full Idea: Maybe there is a class of beliefs that plays a special role in the explanation of action. We have argued against the existence of such a class (or at least any interesting such class). | |
From: Cappelen,H/Dever,Josh (The Inessential Indexical [2013], 06.2) | |
A reaction: The main class which has been proposed is the one that involves indexical beliefs. I agree with this idea. |