30 ideas
| 17082 | Paradox: why do you analyse if you know it, and how do you analyse if you don't? [Ruben] |
| Full Idea: The alleged paradox of analysis asserts that if one knew what was involved in the concept, one would not need the analysis; if one did not know what was involved in the concept, no analysis could be forthcoming. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 1) | |
| A reaction: This is the sort of problem that seemed to bug Plato a lot. You certainly can't analyse something if you don't understand it, but it seems obvious that you can illuminatingly analyse something of which you have a reasonable understanding. |
| 18009 | Chomsky established the view that category mistakes are well-formed but meaningless [Chomsky, by Magidor] |
| Full Idea: The view of Chomsky in 1957 that category mistakes are syntactically well-formed but meaningless is a very standard one. | |
| From: report of Noam Chomsky (Syntactic Structure [1957]) by Ofra Magidor - Category Mistakes 1.3 | |
| A reaction: I'm going off the idea that they are meaningless, largely because I am beginning to sympathise with the view that any composition of meaningful components is meaningful (even if blatantly false). |
| 17087 | The 'symmetry thesis' says explanation and prediction only differ pragmatically [Ruben] |
| Full Idea: The 'symmetry thesis' holds that there is only a pragmatic, or epistemic, but no logical, difference between explaining and predicting. …The only difference is in what the producer of the deduction knows just before the deduction is produced. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 4) | |
| A reaction: He cites Mill has holding this view. It seems elementary to me that I can explain something but not predict it, or predict it but not explain it. The latter case is just Humean habitual induction. |
| 17081 | Usually explanations just involve giving information, with no reference to the act of explanation [Ruben] |
| Full Idea: Plato, Aristotle, Mill and Hempel believed that an explanatory product can be characterized solely in terms of the kind of information it conveys, no reference to the act of explaining being required. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 1) | |
| A reaction: Achinstein says it's about acts, because the same information could be an explanation, or a critique, or some other act. Ruben disagrees, and so do I. |
| 17092 | An explanation needs the world to have an appropriate structure [Ruben] |
| Full Idea: Objects or events in the world must really stand in some appropriate 'structural' relation before explanation is possible. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 7) | |
| A reaction: An important point. These days people talk of 'dependence relations'. Some sort of structure to reality (mainly imposed by the direction of time and causation, I would have thought) is a prerequisite of finding a direction to explanation. |
| 17090 | Most explanations are just sentences, not arguments [Ruben] |
| Full Idea: Typically, full explanations are not arguments, but singular sentences, or conjunctions thereof. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 6) | |
| A reaction: This is mainly objecting to the claim that explanations are deductions from laws and facts. I agree with Ruben. Explanations are just information, I think. Of course, Aristotle's demonstrations are arguments. |
| 17094 | The causal theory of explanation neglects determinations which are not causal [Ruben] |
| Full Idea: The fault of the causal theory of explanation was to overlook the fact that there are more ways of making something what it is or being responsible for it than by causing it. …Causation is a particular type of determinative relation. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 7) | |
| A reaction: The only thing I can think of is that certain abstract facts are 'determined' by other abtract facts, without being 'caused' by them. A useful word. |
| 17088 | Reducing one science to another is often said to be the perfect explanation [Ruben] |
| Full Idea: The reduction of one science to another has often been taken as paradigmatic of explanation. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 5) | |
| A reaction: It seems fairly obvious that the total reduction of chemistry to physics would involve the elimination of all the current concepts of chemistry. Could this possibly enhance our understanding of chemistry? I would have thought not. |
| 17089 | Facts explain facts, but only if they are conceptualised or named appropriately [Ruben] |
| Full Idea: Facts explain facts only when the features and the individuals the facts are about are appropriately conceptualized or named. | |
| From: David-Hillel Ruben (Explaining Explanation [1990], Ch 5) | |
| A reaction: He has a nice example that 'Cicero's speeches stop in 43 BCE' isn't explained by 'Tully died then', if you don't know that Cicero was Tully. Ruben is not defending pragmatic explanation, but to this extent he must be right. |
| 6649 | Chomsky now says concepts are basically innate, as well as syntax [Chomsky, by Lowe] |
| Full Idea: Chomsky now contends that not only the syntax of natural language but also the concepts expressible in it have an innate basis. | |
| From: report of Noam Chomsky (Chomsky on himself [1994]) by E.J. Lowe - Introduction to the Philosophy of Mind Ch.7 n25 | |
| A reaction: This seems to follow Fodor, who has been mocked for implying that we have an innate idea of a screwdriver etc. Note that Chomsky says concepts have an innate 'basis'. This fits well with modern (cautious) rationalism, with which I am happy. |
| 18007 | Syntax is independent of semantics; sentences can be well formed but meaningless [Chomsky, by Magidor] |
| Full Idea: In 1957 Chomsky argues that syntax is an independent field from semantics. …To support this claim he argues that the now-famous category mistake 'Colourless green ideas sleep furiously' is grammatical but meaningless. | |
| From: report of Noam Chomsky (Syntactic Structure [1957]) by Ofra Magidor - Category Mistakes 1.3 | |
| A reaction: I'm tempted by the thought that this famous sentence actually is meaningful, although the meaning is fragmentary, and any proposition which can be assembled from it appears to be blatantly false. |
| 18006 | Chomsky's 'interpretative semantics' says syntax comes first, and is then interpreted [Chomsky, by Magidor] |
| Full Idea: Chomsky and his followers (whose position was labelled 'interpretative semantics') claimed that a sentence is first assigned a syntactic structure by an autonomous syntactic module, and this structure is then provided as input for semantic interpretation. | |
| From: report of Noam Chomsky (Aspects of the Theory of Syntax [1965]) by Ofra Magidor - Category Mistakes 1.3 | |
| A reaction: This certainly doesn't fit the experience of introspecting speech, but then I suppose good pianists focus entirely on the music, and overlook the finger movements which have obvious priority. But I don't know the syntax of the sentence when I begin it. |
| 20624 | Work degrades into heat, but not vice versa [Close] |
| Full Idea: William Thomson, Lord Kelvin, declared (in 1865) the second law of thermodynamics: mechanical work inevitably tends to degrade into heat, but not vice versa. | |
| From: Frank Close (Theories of Everything [2017], 3 'Perpetual') | |
| A reaction: The basis of entropy, which makes time an essential part of physics. Might this be the single most important fact about the physical world? |
| 20623 | First Law: energy can change form, but is conserved overall [Close] |
| Full Idea: The first law of thermodynamics : energy can be changed from one form to another, but is always conserved overall. | |
| From: Frank Close (Theories of Everything [2017], 3 'Perpetual') | |
| A reaction: So we have no idea what energy is, but we know it's conserved. (Daniel Bernoulli showed the greater the mean energy, the higher the temperature. James Joule showed the quantitative equivalence of heat and work p.26-7) |
| 20625 | Third Law: total order and minimum entropy only occurs at absolute zero [Close] |
| Full Idea: The third law of thermodynamics says that a hypothetical state of total order and minimum entropy can be attained only at the absolute zero temperature, minus 273 degrees Celsius. | |
| From: Frank Close (Theories of Everything [2017], 3 'Arrow') | |
| A reaction: If temperature is energetic movement of atoms (or whatever), then obviously zero movement is the coldest it can get. So is absolute zero an energy state, or an absence of energy? I have no idea what 'total order' means. |
| 20622 | All motions are relative and ambiguous, but acceleration is the same in all inertial frames [Close] |
| Full Idea: There is no absolute state of rest; only relative motions are unambiguous. Contrast this with acceleration, however, which has the same magnitude in all inertial frames. | |
| From: Frank Close (Theories of Everything [2017], 3 'Newton's') | |
| A reaction: It seems important to remember this, before we start trumpeting about the whole of physics being relative. ....But see Idea 20634! |
| 20628 | The electric and magnetic are tightly linked, and viewed according to your own motion [Close] |
| Full Idea: Electric and magnetic phenomena are profoundly intertwined; what you interpret as electric or magnetic thus depends on your own motion. | |
| From: Frank Close (Theories of Everything [2017], 3 'Light!') | |
| A reaction: This sounds like an earlier version of special relativity. |
| 20635 | The general relativity equations relate curvature in space-time to density of energy-momentum [Close] |
| Full Idea: The essence of general relativity relates 'curvature in space-time' on one side of the equation to the 'density of momentum and energy' on the other. ...In full, Einstein required ten equations of this type. | |
| From: Frank Close (Theories of Everything [2017], 5 'Gravity') | |
| A reaction: Momentum involves mass, and energy is equivalent to mass (e=mc^2). |
| 20627 | Electric fields have four basic laws (two by Gauss, one by Ampère, one by Faraday) [Close] |
| Full Idea: Four basic laws of electric and magnetic fields: Gauss's Law (about the flux produced by a field), Gauss's law of magnets (there can be no monopoles), Ampère's Law (fields on surfaces), and Farday's Law (accelerated magnets produce fields). | |
| From: Frank Close (Theories of Everything [2017], 3 'Light!') | |
| A reaction: [Highly compressed, for an overview. Close explains them] |
| 20630 | Light isn't just emitted in quanta called photons - light is photons [Close] |
| Full Idea: Planck had assumed that light is emitted in quanta called photons. Einstein went further - light is photons. | |
| From: Frank Close (Theories of Everything [2017], 3 'Light!') | |
| A reaction: The point is that light travels as entities which are photons, rather than the emissions being quantized packets of some other stuff. |
| 20637 | In general relativity the energy and momentum of photons subjects them to gravity [Close] |
| Full Idea: In Einstein's general theory, gravity acts also on energy and momentum, not simply on mass. For example, massless photons of light feel the gravitational attraction of the Sun and can be deflected. | |
| From: Frank Close (Theories of Everything [2017], 5 'Planck') | |
| A reaction: Ah, a puzzle solved. How come massless photons are bent by gravity? |
| 20629 | Electro-magnetic waves travel at light speed - so light is electromagnetism! [Close] |
| Full Idea: Faradays' measurements predicted the speed of electro-magnetic waves, which happened to be the speed of light, so Maxwell made an inspired leap: light is an electromagnetic wave! | |
| From: Frank Close (Theories of Everything [2017], 3 'Light!') | |
| A reaction: Put that way, it doesn't sound like an 'inspired' leap, because travelling at exactly the same speed seems a pretty good indication that they are the same sort of thing. (But I'm not denying that Maxwell was a special guy!) |
| 20632 | In QED, electro-magnetism exists in quantum states, emitting and absorbing electrons [Close] |
| Full Idea: Dirac created quantum electrodynamics (QED): the universal electro-magnetic field can exist in discreet states of energy (with photons appearing and disappearing by energy excitations. This combined classical ideas, quantum theory and special relativity. | |
| From: Frank Close (Theories of Everything [2017], 3 'Light!') | |
| A reaction: Close says this is the theory of everything in atomic structure, but not in nuclei (which needs QCD and QFD). So if there are lots of other 'fields' (e.g. gravitational, weak, strong, Higgs), how do they all fit together? Do they talk to one another? |
| 20642 | Photon exchange drives the electro-magnetic force [Close] |
| Full Idea: The exchange of photons drives the electro-magnetic force. | |
| From: Frank Close (Theories of Everything [2017], 6 'Superstrings') | |
| A reaction: So light, which we just think of as what is visible, is a mere side-effect of the engine room of nature - the core mechanism of the whole electro-magnetic field. |
| 20639 | Quantum fields contain continual rapid creation and disappearance [Close] |
| Full Idea: Quantum field theory implies that the vacuum of space is filled with particles and antiparticles which bubble in and out of existence on faster and faster timescales over shorter and shorter distances. | |
| From: Frank Close (Theories of Everything [2017], 6 'Intro') | |
| A reaction: Ponder this sentence until you head aches. Existence, but not as we know it, Jim. Close says calculations in QED about the electron confirm this. |
| 20631 | Dirac showed how electrons conform to special relativity [Close] |
| Full Idea: In 1928 Paul Dirac discovered the quantum equation that describes the electron and conforms to the requirements special relativity theory. | |
| From: Frank Close (Theories of Everything [2017], 3 'Light!') | |
| A reaction: This sounds like a major step in the unification of physics. Quantum theory and General relativity remain irreconcilable. |
| 20641 | Electrons get their mass by interaction with the Higgs field [Close] |
| Full Idea: The electron gets its mass by interaction with the ubiquitous Higgs field. | |
| From: Frank Close (Theories of Everything [2017], 6 'Hierarchy') | |
| A reaction: I thought I understood mass until I read this. Is it just wrong to say the mass of a table is the 'amount of stuff' in it? |
| 20626 | Modern theories of matter are grounded in heat, work and energy [Close] |
| Full Idea: The link between temperature, heat, work and energy is at the root of our historical ability to construct theories of matter, such as Newton's dynamics, while ignoring, and indeed being ignorant of - atomic dimensions. | |
| From: Frank Close (Theories of Everything [2017], 3 'Arrow') | |
| A reaction: That is, presumably, that even when you fill in the atoms, and the standard model of physics, these aspects of matter do the main explaiining (of the behaviour, rather than of the structure). |
| 20633 | The Higgs field is an electroweak plasma - but we don't know what stuff it consists of [Close] |
| Full Idea: In 2012 it was confirmed that we are immersed in an electroweak plasma - the Higgs field. We curently have no knowledge of what this stuff might consist of. | |
| From: Frank Close (Theories of Everything [2017], 4 'Higgs') | |
| A reaction: The second sentence has my full attention. So we don't understand a field properly until we understand the 'stuff' it is made of? So what are all the familiar fields made of? Tell me more! |
| 20640 | Space-time is indeterminate foam over short distances [Close] |
| Full Idea: At very short distances, space-time itself becomes some indeterminate foam. | |
| From: Frank Close (Theories of Everything [2017], 6 'Intro') | |
| A reaction: [see Close for a bit more detail of this weird idea] |