19 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) |
| 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) |
| 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'. |
| 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. |
| 12219 | Whether a modal claim is true depends on how the object is described [Quine, by Fine,K] |
| Full Idea: Quine says if ∃x□(x>7) makes sense, then for which object x is the condition rendered true? Specify it as '9' and it is apparently rendered true, specify it as 'the number of planets' and it is apparently rendered false. | |
| From: report of Willard Quine (Three Grades of Modal Involvement [1953]) by Kit Fine - Quine on Quantifying In p.105 | |
| A reaction: This is normally characterised as Quine saying that only de dicto involvement is possible, and not de re involvement. Or that that all essences are nominal, and cannot be real. |
| 10922 | Objects are the values of variables, so a referentially opaque context cannot be quantified into [Quine] |
| Full Idea: The objects of a theory are not properly describable as the things named by the singular terms; they are the values, rather, of the variables of quantification. ..So a referentially opaque context is one that cannot properly be quantified into. | |
| From: Willard Quine (Three Grades of Modal Involvement [1953], p.174) | |
| A reaction: The point being that you cannot accurately pick out the objects in the domain |
| 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] |
| 10923 | Aristotelian essentialism says a thing has some necessary and some non-necessary properties [Quine] |
| Full Idea: What Aristotelian essentialism says is that you can have open sentences Fx and Gx, such that ∃x(nec Fx.Gx.Źnec Gx). For example, ∃x(nec(x>5). there are just x planets. Źnec(there are just x planets)). | |
| From: Willard Quine (Three Grades of Modal Involvement [1953], p.176) | |
| A reaction: This is a denial of 'maximal essentialism', that all of a things properties might be essential. Quine is thus denying necessity, except under a description. He may be equivocating over the reference of 'there are just 9 planets'. |
| 10921 | Necessity can attach to statement-names, to statements, and to open sentences [Quine] |
| Full Idea: Three degrees necessity in logic or semantics: first and least is attaching a semantical predicate to the names of statements (as Nec '9>5'); second and more drastic attaches to statements themselves; third and gravest attaches to open sentences. | |
| From: Willard Quine (Three Grades of Modal Involvement [1953], p.158) |
| 10924 | Necessity is in the way in which we say things, and not things themselves [Quine] |
| Full Idea: Necessity resides in the way in which we say things, and not in the things we talk about. | |
| From: Willard Quine (Three Grades of Modal Involvement [1953], p.176) | |
| A reaction: This is a culminating idea of Quine's thoroughgoing empiricism, as filtered through logical positivism. I would hardly dare to accuse Quine of a use/mention confusion (his own bęte noir), but one seems to me to be lurking here. |
| 14804 | Is chance just unknown laws? But the laws operate the same, whatever chance occurs [Peirce] |
| Full Idea: Chance is the name for some law that is unknown to us? If you say 'each die moves under the influence of precise mechanical laws', it seems to me it is not these laws which made the tie turn up sixes, for the laws act the same when other throws come up. | |
| From: Charles Sanders Peirce (The Doctrine of Necessity Examined [1892], p.333) |
| 14805 | Is there any such thing as death among the lower organisms? [Peirce] |
| Full Idea: Among some of the lower organisms, it is a moot point with biologists whether there be anything which ought to be called death. | |
| From: Charles Sanders Peirce (The Doctrine of Necessity Examined [1892], p.334) | |
| A reaction: The point, presumably, is that one phase of an organisms moves into another, and the 'individuals' are not distinct enough for their 'death' to be a significant transition. A nicely mind-expanding thought. |
| 14806 | If the world is just mechanical, its whole specification has no more explanation than mere chance [Peirce] |
| Full Idea: The mechanical philosopher leaves the whole specification of the world utterly unaccounted for, which is pretty nearly as bad as to baldly attribute it to chance. | |
| From: Charles Sanders Peirce (The Doctrine of Necessity Examined [1892], p.337) | |
| A reaction: If now complete is even remotely available, then that doesn't seem to matter too much, but if there is one message modern physics teaches philosophy, it is that we should not give up on trying to answer the deeper questions. |
| 14803 | The more precise the observations, the less reliable appear to be the laws of nature [Peirce] |
| Full Idea: Try to verify any law of nature, and you will find that the more precise your observations, the more certain they will be to show irregular departures from the law. | |
| From: Charles Sanders Peirce (The Doctrine of Necessity Examined [1892], p.331) | |
| A reaction: This nicely encapsulates modern doubts about whether the so-called 'laws' of nature actually capture what is going on in the real world. |