35 ideas
| 18696 | The vagueness of truthmaker claims makes it easier to run anti-realist arguments [Button] |
| Full Idea: The sheer lack of structure demanded by truthmaker theorists means that it is easier to run model-theoretic arguments against them than against correspondence theorists. | |
| From: Tim Button (The Limits of Reason [2013], 02.3) | |
| A reaction: Truthmaking is a vague relation, where correspondence is fairly specific. Model arguments say you can keep the sentences steady, but shuffle around what they refer to. |
| 18701 | The coherence theory says truth is coherence of thoughts, and not about objects [Button] |
| Full Idea: According to the coherence theory of truth, for our thoughts to be true is not for them to be about objects, but only for them to cohere with one another. This is rather terrifying. | |
| From: Tim Button (The Limits of Reason [2013], 14.2) | |
| A reaction: Davidson espoused this view in 1983, but then gave it up. It strikes me as either a daft view of truth, or a denial of truth. The coherence theory of justification, on the other hand, is correct. |
| 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) |
| 18694 | Permutation Theorem: any theory with a decent model has lots of models [Button] |
| Full Idea: The Permutation Theorem says that any theory with a non-trivial model has many distinct isomorphic models with the same domain. | |
| From: Tim Button (The Limits of Reason [2013], 02.1) | |
| A reaction: This may be the most significant claim of model theory, since Putnam has erected an argument for anti-realism on it. See the ideas of Tim Button. |
| 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. |
| 18692 | Realists believe in independent objects, correspondence, and fallibility of all theories [Button] |
| Full Idea: External realists have three principles: Independence - the world is objects that are independent of mind, language and theory; Correspondence - truth involves some correspondence of thoughts and things; Cartesian - an ideal theory might be false. | |
| From: Tim Button (The Limits of Reason [2013], 01.1-3) | |
| A reaction: [compressed; he cites Descartes's Demon for the third] Button is setting these up as targets. I subscribe to all three, in some form or other. Of course, as a theory approaches the success implying it is 'ideal', it becomes highly likely to be accurate. |
| 18693 | Indeterminacy arguments say if a theory can be made true, it has multiple versions [Button] |
| Full Idea: Indeterminacy arguments aim to show that if there is any way to make a theory true, then there are many ways to do so. | |
| From: Tim Button (The Limits of Reason [2013], 02.1) | |
| A reaction: Button says the simplest indeterminacy argument is Putnam's Permutation Argument - that you can shuffle the objects in a formal model, without affecting truth. But do we belief that metaphysics can be settled in this sort of way? |
| 18695 | An ideal theory can't be wholly false, because its consistency implies a true model [Button] |
| Full Idea: If realists think an ideal theory could be false, then the theory is consistent, and hence complete, and hence finitely modellable, and hence it is guaranteed that there is some way to make it true. | |
| From: Tim Button (The Limits of Reason [2013], 02.2) | |
| A reaction: [compressed] This challenges the realists' supposed claim that even the most ideal of theories could possibly be false. Presumably for a theory to be 'ideal' is not all-or-nothing. Are we capable of creating a fully ideal theory? [Löwenheim-Skolem] |
| 1212 | Replacing timbers on Theseus' ship was the classic illustration of the problem of growth and change [Plutarch] |
| Full Idea: At intervals they removed old timbers from the preserved ship and replaced them with sound ones, so the ship became a classic illustration for the philosophers of the disputed question of growth and change, some saying it was the same, others different. | |
| From: Plutarch (Life of Theseus [c.85], 23) |
| 5958 | The sun is always bright; it doesn't become bright when it emerges [Plutarch] |
| Full Idea: The sun doesn't become bright when it emerges from the clouds; it always is bright. | |
| From: Plutarch (26: Oracles in Decline [c.85], §39) | |
| A reaction: Not an argument, but a nice appeal to common sense, like Russell's example of the cat that disappears behind the furniture and then reappears. To disagree with Plutarch here strikes me as the road to philosophical absurdity. |
| 18700 | Cartesian scepticism doubts what is true; Kantian scepticism doubts that it is sayable [Button] |
| Full Idea: Cartesian scepticism agonises over whether our beliefs are true or false, whereas Kantian scepticism agonises over how it is even possible for beliefs to be true or false. | |
| From: Tim Button (The Limits of Reason [2013], 07.2) | |
| A reaction: Kant's question is, roughly, 'how can our thoughts succeed in being about the world?' Kantian scepticism is the more drastic, and looks vulnerable to a turning of the tables, but asking how Kantian worries can even be expressed. |
| 18698 | Predictions give the 'content' of theories, which can then be 'equivalent' or 'adequate' [Button] |
| Full Idea: The empirical 'content' of a theory is all its observable predictions. Two theories with the same predictions are empirically 'equivalent'. A theory which gets it all right at this level is empirically 'adequate'. | |
| From: Tim Button (The Limits of Reason [2013], 05.1) |
| 5959 | Some philosophers say the soul is light [Plutarch] |
| Full Idea: Some philosophers hold that the soul is in its essence light. | |
| From: Plutarch (75: Is 'Live Unknown' a Wise Precept? [c.85], §6) | |
| A reaction: A nice idea, to rival the stoic view that the soul is fire. It is understandable to propose that the soul is some sort of lightweight and fast moving matter. How else could thought be achieved physically? Nowadays, parallel processing is our only model. |
| 5960 | When the soul is intelligent and harmonious, it is part of god and derives from god [Plutarch] |
| Full Idea: The soul, when it has partaken of intelligence and reason and concord, is not merely a work but also a part of god and has come to be not by his agency but both from him as source and out of his substance. | |
| From: Plutarch (67: Platonic Questions [c.85], II.1001) | |
| A reaction: A most intriguing shift of view from earlier concepts of the psuché. How did this come about? This man is a pagan. The history is in the evolution of Platonism. See 'The Middle Platonists' by John Dillon. Davidson is also very impressed by reason. |
| 5952 | Rather than being the whole soul, maybe I am its chief part? [Plutarch] |
| Full Idea: Is each of us not the soul, but the chief part of the soul, by which we think and reason and act, all the other parts of soul as well as of body being mere instruments of its power? | |
| From: Plutarch (74: Reply to Colotes [c.85], §1119) | |
| A reaction: Socrates is associated with the idea that I am my whole soul (Idea 1650). Plutarch represents an interesting development, which may lead both to the Christian 'soul' and to the Cartesian 'ego'. I think Plutarch is right, but what is the 'soul'? |
| 5951 | If atoms have no qualities, they cannot possibly produce a mind [Plutarch] |
| Full Idea: Perception, mind, intelligence and thought cannot so much as be conceived, even with the best will, as arising among void and atoms, things which taken separately have no quality. | |
| From: Plutarch (74: Reply to Colotes [c.85], §1112) | |
| A reaction: A nice articulation of the intuition of all anti-physicalists. Plutarch would have to rethink his position carefully if he learned of the sheer number of connections in the brain, and of the theory of natural selection. His challenge remains, though. |
| 5963 | Some say emotion is a sort of reason, and others say virtue concerns emotion [Plutarch] |
| Full Idea: Some philosophers make the emotions varieties of reason, on the ground that all desire and grief and anger are judgments, while others declare that the virtues have to do with emotions, as when fear is the province of courage. | |
| From: Plutarch (68: Generation of the soul in 'Timaeus' [c.85], 1025d) | |
| A reaction: The second idea comes from Aristotle, but the second is interesting, and corresponds to the views coming from modern neuroscience, where even the most basic thought seems to involve emotion. What could be the motivation for 'pure' reason? |
| 18697 | A sentence's truth conditions are all the situations where it would be true [Button] |
| Full Idea: A sentence's truth conditions comprise an exhaustive list of the situations in which that sentence would be true. | |
| From: Tim Button (The Limits of Reason [2013], 03.4) | |
| A reaction: So to know its meaning you must know those conditions? Compare 'my cat is licking my finger' with 'dramatic events are happening in Ethiopia'. It should take an awful long time to grasp the second sentence. |
| 20796 | Action needs an affinity for a presentation, and an impulse toward the affinity [Plutarch] |
| Full Idea: The sceptics say there are three movements of the soul: presentation, impulse and assent. …And action requires two things: a presentation of something to which one has an affinity, and an impulse toward what is presented as an object of affinity. | |
| From: Plutarch (74: Reply to Colotes [c.85], 1122c) | |
| A reaction: Not much reasoning involved in this account, which the sceptics say is compatible with suspension of judgement. |
| 1477 | Being manly and brave is the result of convention, not of human nature [Plutarch] |
| Full Idea: Manliness is not a natural human attribute, otherwise women would be just as brave. It is due to pressure from laws, and this pressure has no free will, but is a slave of convention and criticism. | |
| From: Plutarch (64: Gryllus - on Rationality in Animals [c.85], 988c) | |
| A reaction: This is the first glimmerings of seeing gender as a cultural creation, rather than as a fact. Presumably he takes the same view of some of the supposed feminine virtues. |
| 1478 | Animals don't value pleasure, as they cease sexual intercourse after impregnation [Plutarch] |
| Full Idea: Animals of both sexes cease to have intercourse after impregnation; that shows how little animals value pleasure, and that nature is all that counts. | |
| From: Plutarch (64: Gryllus - on Rationality in Animals [c.85], 990d) | |
| A reaction: A famous monkey had an implant to stimulate pleasure, and a button to trigger it. It apparently would have starved to death rather than release the button. Animal sex is dull? |
| 5948 | The good life involves social participation, loyalty, temperance and honesty [Plutarch] |
| Full Idea: To live the good life is to live a life of participation in society, of loyalty to friends, of temperance and honest dealing. | |
| From: Plutarch (74: Reply to Colotes [c.85], §1108) | |
| A reaction: 'Participation in society' is the interesting one. This might translate as 'doing your duty', or as 'leading a well-rounded life'. Solitude is wrong if you are indebted to others, and it is unhealthy if you are not. Is solitude really immoral, though? |
| 1479 | Animals have not been led into homosexuality, because they value pleasure very little [Plutarch] |
| Full Idea: Because animals value pleasure very little, they have not been led into sex between males or between females. | |
| From: Plutarch (64: Gryllus - on Rationality in Animals [c.85], 990d) |
| 5950 | If only atoms exist, how do qualities arise when the atoms come together? [Plutarch] |
| Full Idea: If you accept atomism, you must show how bodies without quality have given rise to qualities of every kind by the mere fact of coming together. For example, how has the quality called 'hot' been imposed on the atoms? | |
| From: Plutarch (74: Reply to Colotes [c.85], §1111) | |
| A reaction: This argument is still significant in current philosophy of mind. If temperature is 'mean kinetic energy', you are left wondering where the energy came from, and why minds experience the heat. This is the 'Hard Question'. |
| 5974 | People report seeing through rocks, or over the horizon, or impossibly small works [Plutarch] |
| Full Idea: It is said that Lynceus could see through rock and tree, and a lookout in Sicily saw Carthaginian ships a day and a half away, and Callicrates and Myrmecides are said to fashion carriages canopied with the wings of fly, and write on sesame seeds. | |
| From: Plutarch (72: Against Stoics on common Conceptions [c.85], 1083e) | |
| A reaction: A warning from Plutarch against believing everything you hear! |
| 5957 | Absurd superstitions make people atheist, not disharmony in nature [Plutarch] |
| Full Idea: Men have never thought the universe godless on the ground of detecting some fault in stars or seasons; ..it is the ridiculous things that superstition does that makes people say it would be better if there were no gods at all. | |
| From: Plutarch (14: Superstition [c.85], §12) | |
| A reaction: Not true, I would say. Absurd superstitions do discredit belief in the supernatural, but earthquakes are a disharmony in nature, and a nasty one at that. Nowadays we have other explanations to rival those of religion. |
| 5955 | No one will ever find a city that lacks religious practices [Plutarch] |
| Full Idea: A city without holy places and gods, without any observance of prayers, oaths, oracles, sacrifices for blessings received or rites to avert evils, no traveller has ever seen or will ever see. | |
| From: Plutarch (74: Reply to Colotes [c.85], §1125) | |
| A reaction: The nearest you might get would be Soviet Moscow, but in 1973 I saw a man there jeering at a woman who was kneeling in the street outside a closed church. Plutarch would be stunned at the decline in religious practices in modern Europe. |