14 ideas
| 10688 | 'Equivocation' is when terms do not mean the same thing in premises and conclusion [Beall/Restall] |
| Full Idea: 'Equivocation' is when the terms do not mean the same thing in the premises and in the conclusion. | |
| From: JC Beall / G Restall (Logical Consequence [2005], Intro) |
| 10690 | Formal logic is invariant under permutations, or devoid of content, or gives the norms for thought [Beall/Restall] |
| Full Idea: Logic is purely formal either when it is invariant under permutation of object (Tarski), or when it has totally abstracted away from all contents, or it is the constitutive norms for thought. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) | |
| A reaction: [compressed] The third account sounds rather woolly, and the second one sounds like a tricky operation, but the first one sounds clear and decisive, so I vote for Tarski. |
| 10691 | Logical consequence needs either proofs, or absence of counterexamples [Beall/Restall] |
| Full Idea: Technical work on logical consequence has either focused on proofs, where validity is the existence of a proof of the conclusions from the premises, or on models, which focus on the absence of counterexamples. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 10695 | Logical consequence is either necessary truth preservation, or preservation based on interpretation [Beall/Restall] |
| Full Idea: Two different views of logical consequence are necessary truth-preservation (based on modelling possible worlds; favoured by Realists), or truth-preservation based on the meanings of the logical vocabulary (differing in various models; for Anti-Realists). | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) | |
| A reaction: Thus Dummett prefers the second view, because the law of excluded middle is optional. My instincts are with the first one. |
| 10689 | A step is a 'material consequence' if we need contents as well as form [Beall/Restall] |
| Full Idea: A logical step is a 'material consequence' and not a formal one, if we need the contents as well as the structure or form. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 2) |
| 10696 | A 'logical truth' (or 'tautology', or 'theorem') follows from empty premises [Beall/Restall] |
| Full Idea: If a conclusion follows from an empty collection of premises, it is true by logic alone, and is a 'logical truth' (sometimes a 'tautology'), or, in the proof-centred approach, 'theorems'. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 4) | |
| A reaction: These truths are written as following from the empty set Φ. They are just implications derived from the axioms and the rules. |
| 10693 | Models are mathematical structures which interpret the non-logical primitives [Beall/Restall] |
| Full Idea: Models are abstract mathematical structures that provide possible interpretations for each of the non-logical primitives in a formal language. | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 10692 | Hilbert proofs have simple rules and complex axioms, and natural deduction is the opposite [Beall/Restall] |
| Full Idea: There are many proof-systems, the main being Hilbert proofs (with simple rules and complex axioms), or natural deduction systems (with few axioms and many rules, and the rules constitute the meaning of the connectives). | |
| From: JC Beall / G Restall (Logical Consequence [2005], 3) |
| 6402 | In 1927, Russell analysed force and matter in terms of events [Russell, by Grayling] |
| Full Idea: In his 'Analysis of Matter' (1927), Russell sought to analyse the chief concepts of physics, such as force and matter, in terms of events. | |
| From: report of Bertrand Russell (The Analysis of Matter [1927]) by A.C. Grayling - Russell Ch.2 | |
| A reaction: My immediate reaction is that this is not very promising, simply because we can always ask why a particular event occurred, and this seems to point to a deeper level in the analysis. See Idea 4779, for example. |
| 14732 | A perceived physical object is events grouped around a centre [Russell] |
| Full Idea: The physical object, as inferred from perception, is a group of events arranged about a centre. | |
| From: Bertrand Russell (The Analysis of Matter [1927], 23) | |
| A reaction: At least I like the active aspect of this definition. You then have to explain what an event is, without mentioning objects. You'd better no mention properties either, since they will probably depend on the dreaded objects. |
| 14733 | An object produces the same percepts with or without a substance, so that is irrelevant to science [Russell] |
| Full Idea: There may be a substance at the centre of an object, but is no reason to think so, since the group of events making up the object will produce exactly the same percepts; so the substance, if there is one, is an abstract possibility irrelevant to science. | |
| From: Bertrand Russell (The Analysis of Matter [1927], 23) | |
| A reaction: All empiricists (as Russell is in this passage) seem to neglect inference to the best explanation. Things can be indirectly testable, and I would say that there are genuine general entities which are too close to abstraction to ever be testable. |
| 6418 | Russell rejected phenomenalism because it couldn't account for causal relations [Russell, by Grayling] |
| Full Idea: Russell reverted to realism when he recognised that the notion of causality is problematic for phenomenalism; things in the world seem to affect one another causally in ways that are difficult to account for properly by mere reports of sense-experiences. | |
| From: report of Bertrand Russell (The Analysis of Matter [1927]) by A.C. Grayling - Russell Ch.3 | |
| A reaction: This is very interesting, and doesn't seem to have been enough to make A.J. Ayer eschew phenomenalism (Idea 5170). Once your metaphysics becomes realist (like Russell), your account of perception and objects has to change too. |
| 15672 | Actions norms are only valid if everyone possibly affected is involved in the discourse [Habermas] |
| Full Idea: Only those action norms are valid to which all possibly affected persons could agree as participants in rational discourse. | |
| From: Jürgen Habermas (Between Facts and Norms [1996], p.107), quoted by James Gordon Finlayson - Habermas Ch.6:79 | |
| A reaction: This remark stands somewhere between Kant and Rawls. The Holocaust stands behind Habermas's philosophy. The thought, I suppose, is that it would never have happened if everybody had been fully involved in the original discourse about it. |
| 21706 | At first matter is basic and known by sense-data; later Russell says matter is constructed [Russell, by Linsky,B] |
| Full Idea: In the beginning Russell's ontology included matter as basic, to be known, however, only by inference from sense-data. By the end he wanted to 'contruct' matter from sense-data. | |
| From: report of Bertrand Russell (The Analysis of Matter [1927]) by Bernard Linsky - Russell's Metaphysical Logic 1 | |
| A reaction: [see also p.133] Russell always seems to have been a robust realist about the external world, but the later view seems a lot less realist than the earlier view. |