33 ideas
| 15647 | Truth definitions don't produce a good theory, because they go beyond your current language [Halbach] |
| Full Idea: It is far from clear that a definition of truth can lead to a philosophically satisfactory theory of truth. Tarski's theorem on the undefinability of the truth predicate needs resources beyond those of the language for which it is being defined. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1) | |
| A reaction: The idea is that you need a 'metalanguage' for the definition. If I say 'p' is a true sentence in language 'L', I am not making that observation from within language L. The dream is a theory confined to the object language. |
| 15649 | In semantic theories of truth, the predicate is in an object-language, and the definition in a metalanguage [Halbach] |
| Full Idea: In semantic theories of truth (Tarski or Kripke), a truth predicate is defined for an object-language. This definition is carried out in a metalanguage, which is typically taken to include set theory or another strong theory or expressive language. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1) | |
| A reaction: Presumably the metalanguage includes set theory because that connects it with mathematics, and enables it to be formally rigorous. Tarski showed, in his undefinability theorem, that the meta-language must have increased resources. |
| 15655 | Should axiomatic truth be 'conservative' - not proving anything apart from implications of the axioms? [Halbach] |
| Full Idea: If truth is not explanatory, truth axioms should not allow proof of new theorems not involving the truth predicate. It is hence said that axiomatic truth should be 'conservative' - not implying further sentences beyond what the axioms can prove. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.3) | |
| A reaction: [compressed] |
| 15654 | If truth is defined it can be eliminated, whereas axiomatic truth has various commitments [Halbach] |
| Full Idea: If truth can be explicitly defined, it can be eliminated, whereas an axiomatized notion of truth may bring all kinds of commitments. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.3) | |
| A reaction: The general principle that anything which can be defined can be eliminated (in an abstract theory, presumably, not in nature!) raises interesting questions about how many true theories there are which are all equivalent to one another. |
| 15650 | Axiomatic theories of truth need a weak logical framework, and not a strong metatheory [Halbach] |
| Full Idea: Axiomatic theories of truth can be presented within very weak logical frameworks which require very few resources, and avoid the need for a strong metalanguage and metatheory. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1) |
| 15648 | Instead of a truth definition, add a primitive truth predicate, and axioms for how it works [Halbach] |
| Full Idea: The axiomatic approach does not presuppose that truth can be defined. Instead, a formal language is expanded by a new primitive predicate of truth, and axioms for that predicate are then laid down. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1) | |
| A reaction: Idea 15647 explains why Halbach thinks the definition route is no good. |
| 15656 | Deflationists say truth merely serves to express infinite conjunctions [Halbach] |
| Full Idea: According to many deflationists, truth serves merely the purpose of expressing infinite conjunctions. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.3) | |
| A reaction: That is, it asserts sentences that are too numerous to express individually. It also seems, on a deflationist view, to serve for anaphoric reference to sentences, such as 'what she just said is true'. |
| 15657 | To prove the consistency of set theory, we must go beyond set theory [Halbach] |
| Full Idea: The consistency of set theory cannot be established without assumptions transcending set theory. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 2.1) |
| 15652 | We can use truth instead of ontologically loaded second-order comprehension assumptions about properties [Halbach] |
| Full Idea: The reduction of 2nd-order theories (of properties or sets) to axiomatic theories of truth may be conceived as a form of reductive nominalism, replacing existence assumptions (for comprehension axioms) by ontologically innocent truth assumptions. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.1) | |
| A reaction: I like this very much, as weeding properties out of logic (without weeding them out of the world). So-called properties in logic are too abundant, so there is a misfit with their role in science. |
| 15651 | Instead of saying x has a property, we can say a formula is true of x - as long as we have 'true' [Halbach] |
| Full Idea: Quantification over (certain) properties can be mimicked in a language with a truth predicate by quantifying over formulas. Instead of saying that Tom has the property of being a poor philosopher, we can say 'x is a poor philosopher' is true of Tom. | |
| From: Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1.1) | |
| A reaction: I love this, and think it is very important. He talks of 'mimicking' properties, but I see it as philosophers mistakenly attributing properties, when actually what they were doing is asserting truths involving certain predicates. |
| 9216 | Each area of enquiry, and its source, has its own distinctive type of necessity [Fine,K] |
| Full Idea: The three sources of necessity - the identity of things, the natural order, and the normative order - have their own peculiar forms of necessity. The three main areas of human enquiry - metaphysics, science and ethics - each has its own necessity. | |
| From: Kit Fine (The Varieties of Necessity [2002], 6) | |
| A reaction: I would treat necessity in ethics with caution, if it is not reducible to natural or metaphysical necessity. Fine's proposal is interesting, but I did not find it convincing, especially in its view that metaphysical necessity doesn't intrude into nature. |
| 9214 | Unsupported testimony may still be believable [Fine,K] |
| Full Idea: I may have good reason to believe some testimony, for example, even though the person providing the testimony has no good reason for saying what he does. | |
| From: Kit Fine (The Varieties of Necessity [2002], 5) | |
| A reaction: Thus small children, madmen and dreamers may occasionally get things right without realising it. I take testimony to be merely one more batch of evidence which has to be assessed in building the most coherent picture possible. |
| 9215 | Causation is easier to disrupt than logic, so metaphysics is part of nature, not vice versa [Fine,K] |
| Full Idea: It would be harder to break P-and-Q implying P than the connection between cause and effect. This difference in strictness means it is more plausible that natural necessities include metaphysical necessities, than vice versa. | |
| From: Kit Fine (The Varieties of Necessity [2002], 6) | |
| A reaction: I cannot see any a priori grounds for the claim that causation is more easily disrupted than logic. It seems to be based on the strategy of inferring possibilities from what can be imagined, which seems to me to lead to wild misunderstandings. |
| 21181 | Relativity and Quantum theory give very different accounts of forces [Hesketh] |
| Full Idea: General Relativity and quantum mechanics are the two great theories in physics today but they give two very different ideas for how forces work. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 01) | |
| A reaction: Relativity says it is space curvature, and quantum theory says it is particle exchange? But is there a Relativity account of the strong nuclear force? |
| 21183 | Thermodynamics introduced work and entropy, to understand steam engine efficiency [Hesketh] |
| Full Idea: The Laws of Thermodynamics introduced the concepts of entropy and work; put simply, how much useful energy you can really get out of a steam engine. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 03) | |
| A reaction: The point of science by this stage was to introduce measurable and quantifiable concepts |
| 21199 | Spinning electric charge produces magnetism, so all fermions are magnets [Hesketh] |
| Full Idea: The muon, like all fermions, spins - and because a spinning electric charge generates a magnetic field all fermions act like tiny bar magnets. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 11) |
| 21191 | Photons are B and W° bosons, linked by the Higgs mechanism [Hesketh] |
| Full Idea: The photon is actually a mix of two deeper things, the B and the W°, tied together by the Higgs mechanism. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 06) | |
| A reaction: The B (for 'Boson') transmits a force associated with the 'winding symmetry'. (I record this without properly understanding it.) |
| 21189 | Electrons may have smaller components, bound by a new force [Hesketh] |
| Full Idea: Quarks, leptons or bosons may actually be made up of something even smaller, bound together by a conjectural new force. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 05) | |
| A reaction: Electrons are a type of lepton. Compare Idea 21180, from the same book. If electrons are not fundamental, what matters is not some 'stuff' they are made of, but a different force that would bind the ingredients. |
| 21180 | Electrons are fundamental and are not made of anything; they are properties without size [Hesketh] |
| Full Idea: As far as we can tell, electrons (and quarks) are fundamental. They are not small lumps of material, because we could always ask what the material is. The electron just ...is. They are collections of properties, with no apparent size. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 01) | |
| A reaction: This idea from physics HAS to be of interest to philosophers! The bundle theory is discredited for normal objects and for minds, and so is the substrate idea for supporting properties. But rigorous physics accepts a bundle theory. |
| 21182 | Quantum mechanics is our only theory, and is very precise, and repeatedly confirmed [Hesketh] |
| Full Idea: Quantum mechanics is the only working description of the universe that we have. It is amazingly precise, and so far every experimental test has verified its predictions. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 02) | |
| A reaction: I take it from this that quantum mechanics is simply TRUE. Get over it! It will never turn out to be wrong, but may be subsumed within some more fine-grained or extensive theory. |
| 21184 | Physics was rewritten to explain stable electron orbits [Hesketh] |
| Full Idea: Explaining the stable electron orbits would require a complete rewriting of the physics of subatomic particles. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 03) | |
| A reaction: This really looks like a simple and major landmark moment. You can ignore a single anomaly, but not a central feature of your entire theory. |
| 21187 | Virtual particles can't be measured, and can ignore the laws of physics [Hesketh] |
| Full Idea: We can never measure these virtual (transitory) particles directly, and it turns out that they don't even have to obey the laws of physics. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 05) | |
| A reaction: These seems to be the real significance of the Uncertainty Principle. Such particles 'borrow' huge amounts of energy for very short times. |
| 21185 | Colour charge is positive or negative, and also has red, green or blue direction [Hesketh] |
| Full Idea: Colour charge is 'three-dimensional'. As well as the charge having a positive or negative sign, it can also have a direction, and for convenience these three different directions (pointing like a weather vane) are labelled 'red', 'green' and 'blue'. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 04) |
| 21194 | The Standard Model omits gravity, because there are no particles involved [Hesketh] |
| Full Idea: Gravity is not included in the Standard Model because we simply cannot study it using particles. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 09) | |
| A reaction: I'm guessing that Einstein describes how gravity behaves, but not what it is. |
| 21195 | In Supersymmetry the Standard Model simplifies at high energies [Hesketh] |
| Full Idea: Supersymmetry suggest that the Standard Model becomes much simpler at high energies. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 10) |
| 21197 | Standard Model forces are one- two- and three-dimensional [Hesketh] |
| Full Idea: The forces in the Standard Model are built on gauge symmetries, with a one-dimensional charge (like electromagnetism), a two-dimensional charge (the weak force), and a three dimensional charge (the strong force). | |
| From: Gavin Hesketh (The Particle Zoo [2016], 10) | |
| A reaction: See also Idea 21185. |
| 21188 | Quarks and leptons have a weak charge, for the weak force [Hesketh] |
| Full Idea: For the weak force there must be a corresponding 'weak charge', and all the fermions, all the quarks and leptons carry it. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 05) | |
| A reaction: So electrons carry a weak charge, as well as an electromagnetic charge. Like owning several passports. |
| 21186 | Quarks rush wildly around in protons, restrained by the gluons [Hesketh] |
| Full Idea: Inside a proton the quarks are rushing around like caged animals, free to move until they push against the bars to try to escape, when the gluons pull them back in. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 04) |
| 21192 | Neutrinos only interact with the weak force, but decays produce them in huge numbers [Hesketh] |
| Full Idea: Neutrinos only interact with the weak force, which means they barely interact at all, but because the weak force is crucial in the decays of so many other particles, neutrinos are still produced in huge numbers. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 08) | |
| A reaction: They only interact with the W and Z bosons. |
| 21196 | To combine the forces, they must all be the same strength at some point [Hesketh] |
| Full Idea: If all the forces are to combine, at some point they must all be the same strength, and Supersymmetry (SuSy) makes this happen. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 10) | |
| A reaction: This sounds like an impressive reason for favouring supersymmetry - as long as you have an a priori preference for everything combining. |
| 21190 | 'Space' in physics just means location [Hesketh] |
| Full Idea: 'Space' in physics really just means location. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 06) | |
| A reaction: Location can, of course, only be specified relative to something else. Space is really an abstraction, but at least it means there is some sort of background to locate all the fundamental fields. |
| 21193 | The universe is 68% dark energy, 27% dark matter, 5% regular matter [Hesketh] |
| Full Idea: The most precise surveys of the stars and galaxies tell us that the universe is made up of 68% dark energy, 27% dark matter, and just 5% regular matter (the stuff of the Standard Model of particle physics). | |
| From: Gavin Hesketh (The Particle Zoo [2016], 09) | |
| A reaction: Regular matter - that's me, that is. |
| 21198 | If a cosmic theory relies a great deal on fine-tuning basic values, it is probably wrong [Hesketh] |
| Full Idea: If a theory has to rely on excessive 'fine-tuning', a series of extremely unlikely events in order to produce the universe we see around us, then it is extremely unlikely that this theory is correct. | |
| From: Gavin Hesketh (The Particle Zoo [2016], 10) | |
| A reaction: He says the Standard Model has 26 parameters which are only known by experiment, rather than by theory. So instead of saying '...so there is a God', we should say '...so our theory isn't very good'. |