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) |
| 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. |
| 1868 | The world was made as much for animals as for man [Celsus] |
| Full Idea: The world was made as much for the irrational animals as for men. | |
| From: Celsus (On the True Doctrine (Against Christians) [c.178], §V) | |
| A reaction: A good remark. It seems to be a classic distortion of European Christianity that the world is made for us, and that animals only exist to fill our sandwiches. |
| 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. |
| 1867 | Christians presented Jesus as a new kind of logos to oppose that of the philosophers [Celsus] |
| Full Idea: Christians put forth this Jesus not only as the son of God, but as the very Logos - not the pure and holy Logos known to the philosophers, but a new kind of Logos. | |
| From: Celsus (On the True Doctrine (Against Christians) [c.178], III) |