15 ideas
| 8868 | Objective truth arises from interpersonal communication [Davidson] |
| Full Idea: The source of the concept of objective truth is interpersonal communication. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.209) | |
| A reaction: This is a distinctively Davidsonian idea, arising out of Wittgenstein's Private Language Argument. We could go a step further, and just say that 'objectivity is a social concept'. Davidson more or less pleads guilty to pragmatism in this essay. |
| 11022 | Gentzen introduced a natural deduction calculus (NK) in 1934 [Gentzen, by Read] |
| Full Idea: Gentzen introduced a natural deduction calculus (NK) in 1934. | |
| From: report of Gerhard Gentzen (works [1938]) by Stephen Read - Thinking About Logic Ch.8 |
| 11065 | The inferential role of a logical constant constitutes its meaning [Gentzen, by Hanna] |
| Full Idea: Gentzen argued that the inferential role of a logical constant constitutes its meaning. | |
| From: report of Gerhard Gentzen (works [1938]) by Robert Hanna - Rationality and Logic 5.3 | |
| A reaction: Possibly inspired by Wittgenstein's theory of meaning as use? This idea was the target of Prior's famous connective 'tonk', which has the role of implying anything you like, proving sentences which are not logical consequences. |
| 11023 | The logical connectives are 'defined' by their introduction rules [Gentzen] |
| Full Idea: The introduction rules represent, as it were, the 'definitions' of the symbols concerned, and the elimination rules are no more, in the final analysis, than the consequences of these definitions. | |
| From: Gerhard Gentzen (works [1938]), quoted by Stephen Read - Thinking About Logic Ch.8 | |
| A reaction: If an introduction-rule (or a truth table) were taken as fixed and beyond dispute, then it would have the status of a definition, since there would be nothing else to appeal to. So is there anything else to appeal to here? |
| 11213 | Each logical symbol has an 'introduction' rule to define it, and hence an 'elimination' rule [Gentzen] |
| Full Idea: To every logical symbol there belongs precisely one inference figure which 'introduces' the symbol ..and one which 'eliminates' it. The introductions represent the 'definitions' of the symbols concerned, and eliminations are consequences of these. | |
| From: Gerhard Gentzen (works [1938], II.5.13), quoted by Ian Rumfitt - "Yes" and "No" III | |
| A reaction: [1935 paper] This passage is famous, in laying down the basics of natural deduction systems of logic (ones using only rules, and avoiding axioms). Rumfitt questions whether Gentzen's account gives the sense of the connectives. |
| 10067 | Gentzen proved the consistency of arithmetic from assumptions beyond arithmetic [Gentzen, by Musgrave] |
| Full Idea: Gentzen proved the consistency of arithmetic from assumptions which transcend arithmetic. | |
| From: report of Gerhard Gentzen (works [1938]) by Alan Musgrave - Logicism Revisited §5 | |
| A reaction: This does not contradict Gödel's famous result, but reinforces it. The interesting question is what assumptions Gentzen felt he had to make. |
| 8867 | A belief requires understanding the distinctions of true-and-false, and appearance-and-reality [Davidson] |
| Full Idea: Having a belief demands in addition appreciating the contrast between true belief and false, between appearance and reality, mere seeming and being. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.209) | |
| A reaction: This sets the bar very high for belief (never mind knowledge), and seems to imply that animals don't have beliefs. How should we describe their cognitive states then? I would say these criteria only apply to actual knowledge. |
| 10347 | Objectivity is intersubjectivity [Davidson] |
| Full Idea: An entity is objective in so far as it is intersubjective. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991]), quoted by Martin Kusch - Knowledge by Agreement Ch.10 | |
| A reaction: This thought baffled me until I saw it in the context of socialised epistemology. Effectively objectivity is subsumed under justification, which in turn is seen in a social context, not private to individuals. |
| 8866 | If we know other minds through behaviour, but not our own, we should assume they aren't like me [Davidson] |
| Full Idea: If the mental states of others are known only through their behavioral and other outward manifestations, while this is not true of our own mental states, why should we think our own mental states are anything like those of others? | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.207) | |
| A reaction: His point is that if you seriously doubt other minds, you should follow through on the implications. But that is to treat it as a theory about other minds, rather an a sceptical worry. Descartes didn't walk into walls while writing Meditation 1. |
| 10346 | Knowing other minds rests on knowing both one's own mind and the external world [Davidson, by Dummett] |
| Full Idea: Davidson argues that knowledge of other minds presupposes knowledge of one's own mind, and that there is no knowledge of other minds without knowledge of the external world. | |
| From: report of Donald Davidson (Three Varieties of Knowledge [1991]) by Michael Dummett - Common Sense and Physics Ch.10 | |
| A reaction: Davidson't argument is actually hard to swallow because it is so long and complex. Compressing the point makes it begin to sound like a variant of the argument from analogy. |
| 8870 | Content of thought is established through communication, so knowledge needs other minds [Davidson] |
| Full Idea: Until a baseline has been established by communication with someone else, there is no point is saying one's own thoughts have a propositional content. Hence knowledge of another mind is essential all thought and all knowledge. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.213) | |
| A reaction: This really is building a skyscraper on the slightly shaky claims of the Private Language Argument (e.g. Idea 4158). Animals are so important in discussions of this kind. Is an albatross more or less devoid of thought and belief? |
| 8869 | The principle of charity attributes largely consistent logic and largely true beliefs to speakers [Davidson] |
| Full Idea: Concerning charity, the Principle of Coherence seeks logical consistency in the thought of the speaker, and the Principle of Correspondence seeks a similar response to features of the world to that of an interpreter. The speaker has logic and true belief. | |
| From: Donald Davidson (Three Varieties of Knowledge [1991], p.211) | |
| A reaction: Davidson adds a Kantian commitment to pure and universal reason to the very sceptical framework created by Quine. I agree with Davidson, but it seems more like faith than like an argument or an empirical observation. |
| 7276 | All art is quite useless [Wilde] |
| Full Idea: All art is quite useless. | |
| From: Oscar Wilde (Preface to 'Dorian Gray' [1891]) | |
| A reaction: Echoes Kant's thought that art is 'purposive without purpose'. Although I find Wilde's claims that morality has nothing to do with art to be naďve, I find this remark sympathetic. Art may play with moral feelings, but is unlikely to affect actions. |
| 7274 | Books are only well or badly written, not moral or immoral [Wilde] |
| Full Idea: There is no such thing as a moral or an immoral book. Books are well written, or badly written. That is all. | |
| From: Oscar Wilde (Preface to 'Dorian Gray' [1891]) | |
| A reaction: This is simply false. Novels that are viciously (or subtly) racist, sexist, homophobic, or egotistical can obviously be immoral. I could write a nasty story about Oscar Wilde. It might, though, be very well written. If life is moral, so are novels. |
| 7275 | Having ethical sympathies is a bad mannerism of style in an artist [Wilde] |
| Full Idea: No artist has ethical sympathies. An ethical sympathy in an artist is an unpardonable mannerism of style. | |
| From: Oscar Wilde (Preface to 'Dorian Gray' [1891]) | |
| A reaction: This has a Nietzschean suggestion that the artist is 'beyond good and evil', and operates on some higher level of values, which in Wilde's case seem to be purely aesthetic. You can't justify a callous murder by executing it beautifully. |