27 ideas
| 19115 | You can 'rebut' an argument's conclusion, or 'undercut' its premises [Antonelli] |
| Full Idea: A 'rebut' of an argument establishes that its conclusion is not the case. An 'undercut' of the argument shows that the premises do not support that conclusion. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 3.2) |
| 19119 | We infer that other objects are like some exceptional object, if they share some of its properties [Antonelli] |
| Full Idea: The exceptional status of an object with respect to some default is more likely to spread to other objects if they share properties with that object that may play a role in explaining the exceptional status. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 4) | |
| A reaction: This is an example of the sort of rational behaviour we exhibit, and which a 'real life' logic would somehow need to capture. I would suggest the essentialist logic designed by Kit Fine as a first port of call. |
| 19111 | Reasoning may be defeated by new premises, or by finding out more about the given ones [Antonelli] |
| Full Idea: Most defeasible reasoning is externally dynamic, affected by the addition of further premises. But there is also an internal (or 'diachronic') dynamic, when further analysis reveals more about the given premises. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 1) |
| 19113 | Weakest Link Principle: prefer the argument whose weakest link is the stronger [Antonelli] |
| Full Idea: In the Weakest Link Principle, an argument is preferred to another conflicting argument if its weakest defeasible link is stronger than the weakest defeasible link in the conflicting argument. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 2.1) | |
| A reaction: [He cites John Pollock 1991] This sounds like the elementary principle applied when choosing a rope by which to hang a large weight above your head. It gets non-monotonic logic off the ground - if you know how to evaluate 'weakest'. |
| 19114 | Should we accept Floating Conclusions, derived from two arguments in conflict? [Antonelli] |
| Full Idea: There is much discussion of whether Floating Conclusions should be derived, given that they were derived from two arguments which conflict with one another. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 2.3) |
| 19116 | Non-monotonic core: Reflexivity, Cut, Cautious Monotonicity, Left Logical Equivalence, Right Weakening [Antonelli] |
| Full Idea: Conservative core of non-monotonic logic:Reflexivity (p proves p), Cut (if p proves q, it proves their joint implications), Cautious Monotonicity, Left Logical Equivalence (equivalences have same consequences), Right Weakening (non-m preserves classical). | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 3.5.1) | |
| A reaction: [Highly compressed, and without symbols] |
| 19117 | We can rank a formula by the level of surprise if it were to hold [Antonelli] |
| Full Idea: We can think of an 'ordinal ranking function' κ([φ)] as the level of surprise we would face were φ to hold, up to maximal surprise. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 3.5.2) | |
| A reaction: This suggests that Bayes's Theorem might be relevant to non-monotonic logic. This suggests that registering surprise would need to be an important feature of robot behaviour. |
| 19118 | People don't actually use classical logic, but may actually use non-monotonic logic [Antonelli] |
| Full Idea: Test subjects seem to perform very poorly in various reasoning tests (Wason Selection, Suppression Task), suggesting logic has a subordinate role, but this may be using classical logic, where non-monotonic logics would be more appropriate. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 4) | |
| A reaction: Fred Sommers presents his Term Logic (based on Aristotle) as closer to how people actually reason. It is certainly crazy to infer that most people's everyday reasoning is irrational. Induction is highly rational; it's just not deductive. |
| 19110 | In classical logic the relation |= has Monotony built into its definition [Antonelli] |
| Full Idea: In classical logic, Monotony follows immediately from the nature of the relation |=, for Γ |= φ holds precisely when φ is true on every interpretation on which all sentences in Γ are true. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 1) | |
| A reaction: That is, semantic consequence (|=) is defined in terms of a sentence (φ) always being true if some other bunch of sentences (Γ) are true. Hence the addition of further sentences to Γ will make no difference - which is Monotony. |
| 19112 | Cautious Monotony ignores proved additions; Rational Monotony fails if the addition's negation is proved [Antonelli] |
| Full Idea: Basic Monotony: something stays proved if further premises are added. Cautious Monotony: the addition of something which has been proved makes no difference. Rational Monotony: it stays proved as long as the addition's negation hasn't been proved. | |
| From: G. Aldo Antonelli (Non-Monotonic Logic [2014], 1) | |
| A reaction: [A compressed and non-symbolic summary] |
| 20189 | Belief is a feeling, independent of the will, which arises from uncontrolled and unknown causes [Hume] |
| Full Idea: Belief consists merely in a certain feeling or sentiment; in something, that depends not on the will, but must arise from certain determinate causes and principles, of which we are not master. | |
| From: David Hume (Treatise of Human Nature, + Appendix [1740], Appen p.2) | |
| A reaction: This is the opposite of Descartes' 'doxastic voluntarism' (i.e. we choose what to believe). If you want to become a Christian, steep yourself in religious literature, and the company of religious people. It will probably work. |
| 21309 | A proposition cannot be intelligible or consistent, if the perceptions are not so [Hume] |
| Full Idea: No proposition can be intelligible or consistent with regard to objects, which is not so with regard to perceptions. | |
| From: David Hume (Treatise of Human Nature, + Appendix [1740], Appendix) | |
| A reaction: An interesting variant on expressions of the empiricist principle. Presumably one can say intelligible things about Escher drawings. |
| 21515 | Incoherence may be more important for enquiry than coherence [Olsson] |
| Full Idea: While coherence may lack the positive role many have assigned to it, ...incoherence plays an important negative role in our enquiries. | |
| From: Erik J. Olsson (Against Coherence [2005], 10.1) | |
| A reaction: [He cites Peirce as the main source for this idea] We can hardly by deeply impressed by incoherence if we have no sense of coherence. Incoherence is just one of many markers for theory failure. Missing the target, bad concepts... |
| 21514 | Coherence is the capacity to answer objections [Olsson] |
| Full Idea: According to Lehrer, coherence should be understood in terms of the capacity to answer objections. | |
| From: Erik J. Olsson (Against Coherence [2005], 9) | |
| A reaction: [Keith Lehrer 1990] We can connect this with the Greek requirement of being able to give an account [logos], which is the hallmark of understanding. I take coherence to be the best method of achieving understanding. Any understanding meets Lehrer's test. |
| 21496 | Mere agreement of testimonies is not enough to make truth very likely [Olsson] |
| Full Idea: Far from guaranteeing a high likelihood of truth by itself, testimonial agreement can apparently do so only if the circumstances are favourable as regards independence, prior probability, and individual credibility. | |
| From: Erik J. Olsson (Against Coherence [2005], 1) | |
| A reaction: This is Olson's main thesis. His targets are C.I.Lewis and Bonjour, who hoped that a mere consensus of evidence would increase verisimilitude. I don't see a problem for coherence in general, since his favourable circumstances are part of it. |
| 21499 | Coherence is only needed if the information sources are not fully reliable [Olsson] |
| Full Idea: An enquirer who is fortunate enough to have at his or her disposal fully reliable information sources has no use for coherence, the need for which arises only in the context of less than fully reliable informations sources. | |
| From: Erik J. Olsson (Against Coherence [2005], 2.6.2) | |
| A reaction: I take this to be entirely false. How do you assess reliability? 'I've seen it with my own eyes'. Why trust your eyes? In what visibility conditions do you begin to doubt your eyes? Why do rational people mistrust their intuitions? |
| 21502 | A purely coherent theory cannot be true of the world without some contact with the world [Olsson] |
| Full Idea: The Input Objection says a pure coherence theory would seem to allow that a system of beliefs be justified in spite of being utterly out of contact with the world it purports to describe, so long as it is, to a sufficient extent, coherent. | |
| From: Erik J. Olsson (Against Coherence [2005], 4.1) | |
| A reaction: Olson seems impressed by this objection, but I don't see how a system could be coherently about the world if it had no known contact with the world. Olson seems to ignore meta-coherence, which evaluates the status of the system being studied. |
| 21512 | Extending a system makes it less probable, so extending coherence can't make it more probable [Olsson] |
| Full Idea: Any non-trivial extension of a belief system is less probable than the original system, but there are extensions that are more coherent than the original system. Hence more coherence does not imply a higher probability. | |
| From: Erik J. Olsson (Against Coherence [2005], 6.4) | |
| A reaction: [Olson cites Klein and Warfield 1994; compressed] The example rightly says the extension could have high internal coherence, but not whether the extension is coherent with the system being extended. |
| 15755 | Hume needs a notion which includes degrees of resemblance [Shoemaker on Hume] |
| Full Idea: Hume needs a notion of resemblance where some things resemble a given thing more than other things do, and some may resemble exactly, and some hardly at all. | |
| From: comment on David Hume (Treatise of Human Nature, + Appendix [1740]) by Sydney Shoemaker - Causality and Properties §02 | |
| A reaction: An astute and simple point. Once you admit degrees of resemblance, of course, then resemblance probably ceases to be a primitive concept in your system, and Hume would be well stuck. |
| 5323 | Experiences are logically separate, but factually linked by simultaneity or a feeling of continuousness [Ayer on Hume] |
| Full Idea: Our experiences are logically independent, but they may be factually connected. What unites them is that either they are experienced together, or (if at separate times) they are separated by a stream of experience which is felt to be continuous. | |
| From: comment on David Hume (Treatise of Human Nature, + Appendix [1740], Bk 3 App.) by A.J. Ayer - The Central Questions of Philosophy §VI.A | |
| A reaction: A strict empiricist cannot deny that the feeling of continuity could be false, though that invites the Cartesian question of what exactly is experiencing the delusion. Hume denies that we experience any link between simultaneous experiences. |
| 21311 | Are self and substance the same? Then how can self remain if substance changes? [Hume] |
| Full Idea: Is the self the same with substance? If it be, how can that question have place concerning the subsistence of self, under a change of substance? If they be distinct, what is the difference between them? | |
| From: David Hume (Treatise of Human Nature, + Appendix [1740], Appendix) | |
| A reaction: Locke seems to think there is a characterless substance which supports momories, and the latter constitute the self. So if my substance acquires Nestor's memories, I become Nestor. Hume, the stricter empiricist, cares nothing for characterless things. |
| 21312 | Perceptions are distinct, so no connection between them can ever be discovered [Hume] |
| Full Idea: If perceptions are distinct existences, they form a whole only by being connected together. But no connexions among distinct existences are ever discoverable. We only feel a connexion ...to pass from one object to another. | |
| From: David Hume (Treatise of Human Nature, + Appendix [1740], Appendix) | |
| A reaction: This first part of this is a problem for any 'bundle' theory of objects or self. This is why Hume abandons all hope for his theory of personal identity based on association. You infer the associations, but don't perceive them. |
| 21308 | We have no impression of the self, and we therefore have no idea of it [Hume] |
| Full Idea: Every idea is derived from preceding impressions; and we have no impression of self or substance, as something simple and individual. We have, therefore, no idea of them in that sense. | |
| From: David Hume (Treatise of Human Nature, + Appendix [1740], Appendix) | |
| A reaction: This spells out with beautiful simplicity how his empiricist assumptions lead him to this sceptical view. No logical positivist could reject this thought. Personally I favour empiricism with added inference to the best explanation. |
| 21310 | Does an oyster with one perception have a self? Would lots of perceptions change that? [Hume] |
| Full Idea: Suppose an oyster to have only one perception, as of thirst or hunger. Do you consider any thing but merely that perception? Have you any notion of self or substance? If not, the addition of other perceptions can never give you that notion. | |
| From: David Hume (Treatise of Human Nature, + Appendix [1740], Appendix) | |
| A reaction: A splendid addition to his earlier sceptical thinking. We could form a different conclusion. Suppose I do have a self. If my multitudinous perceptions were reduced to a single perception of agonising pain, would that remove the self? |
| 23115 | We have no natural love of mankind, other than through various relationships [Hume] |
| Full Idea: It may be affirm'd, that there is no such passion in human minds, as the love of mankind, merely as such, independent of personal qualities, of services, or of relation to ourself. | |
| From: David Hume (Treatise of Human Nature, + Appendix [1740], p.481), quoted by John Kekes - Against Liberalism 9.4 | |
| A reaction: Hume says this is for the best. I can't imagine spontaneous love of human beings we have never met. It takes the teachings of some sort of doctrine - religious or political - to produce such an attitude. I see it as a distortion of love. A hijacking. |
| 16946 | Causation is just invariance, as long as it is described in general terms [Quine on Hume] |
| Full Idea: Hume explained cause as invariable succession, and this makes sense as long as the cause and effect are referred to by general terms. … This account leaves singular causal statements unexplained. | |
| From: comment on David Hume (Treatise of Human Nature, + Appendix [1740]) by Willard Quine - Natural Kinds p.131 | |
| A reaction: A nice 20th century linguistic point made against a good 18th century theory. |
| 15250 | If impressions, memories and ideas only differ in vivacity, nothing says it is memory, or repetition [Whitehead on Hume] |
| Full Idea: Hume confuses 'repetition of impressions' with 'impression of repetitions of impressions'. ...In order of 'force and vivacity' we have: impressions, memories, ideas. This omits the vital fact that memory is memory; the notion of repetition is lost. | |
| From: comment on David Hume (Treatise of Human Nature, + Appendix [1740]) by Alfred North Whitehead - Process and Reality V.II | |
| A reaction: [compressed; Harré and Madden spotted this idea] This seems to pinpoint rather nicely the hopeless thinness of Hume's account. He is so desperate to get it down to minimal empirical experience that his explanations are too thin. One big idea.... |