6 ideas
| 13831 | Logic is based on transitions between sentences [Prawitz] |
| Full Idea: I agree entirely with Dummett that the right way to answer the question 'what is logic?' is to consider transitions between sentences. | |
| From: Dag Prawitz (Gentzen's Analysis of First-Order Proofs [1974], §04) | |
| A reaction: I always protest at this point that reliance on sentences is speciesism against animals, who are thereby debarred from reasoning. See the wonderful Idea 1875 of Chrysippus. Hacking's basic suggestion seems right. Transition between thoughts. |
| 13825 | Natural deduction introduction rules may represent 'definitions' of logical connectives [Prawitz] |
| Full Idea: With Gentzen's natural deduction, we may say that the introductions represent, as it were, the 'definitions' of the logical constants. The introductions are not literally understood as 'definitions'. | |
| From: Dag Prawitz (Gentzen's Analysis of First-Order Proofs [1974], 2.2.2) | |
| A reaction: [Hacking, in 'What is Logic? §9' says Gentzen had the idea that his rules actually define the constants; not sure if Prawitz and Hacking are disagreeing] |
| 13823 | In natural deduction, inferences are atomic steps involving just one logical constant [Prawitz] |
| Full Idea: In Gentzen's natural deduction, the inferences are broken down into atomic steps in such a way that each step involves only one logical constant. The steps are the introduction or elimination of the logical constants. | |
| From: Dag Prawitz (Gentzen's Analysis of First-Order Proofs [1974], 1.1) |
| 3900 | Maybe experience is not essential to perception, but only to the causing of beliefs [Armstrong, by Scruton] |
| Full Idea: Armstrong has argued that experience, as normally understood, is not necessary to perception. To perceive is to acquire beliefs, through a causal process. | |
| From: report of David M. Armstrong (Belief Truth and Knowledge [1973]) by Roger Scruton - Modern Philosophy:introduction and survey 23.4 |
| 4253 | Externalism says knowledge involves a natural relation between the belief state and what makes it true [Armstrong] |
| Full Idea: Externalist accounts of non-inferential knowledge say what makes a true non-inferential belief a case of knowledge is some natural relation which holds between the belief state and the situation which makes the belief true. | |
| From: David M. Armstrong (Belief Truth and Knowledge [1973], 11.III.6) | |
| A reaction: Armstrong's concept is presumably a response to Quine's desire to 'naturalise epistemology'. Bad move, I suspect. It probably reduces knowledge to mere true belief, and hence a redundant concept. |
| 4761 | The 'error theory' of morals says there is no moral knowledge, because there are no moral facts [Mackie, by Engel] |
| Full Idea: Mackie's 'error theory' of ethics says that if a fact is something that corresponds to a true proposition, there are actually no moral facts, hence no knowledge of what moral statements are about. | |
| From: report of J.L. Mackie (Ethics: Inventing Right and Wrong [1977]) by Pascal Engel - Truth §4.2 | |
| A reaction: Personally I am inclined to think that there are moral facts (about what nature shows us constitutes a good human being), based on virtue theory. Mackie is a good warning, though, against making excessive claims. You end up like a bad scientist. |