21 ideas
| 12452 | Our dislike of contradiction in logic is a matter of psychology, not mathematics [Brouwer] |
| Full Idea: Not to the mathematician, but to the psychologist, belongs the task of explaining why ...we are averse to so-called contradictory systems in which the negative as well as the positive of certain propositions are valid. | |
| From: Luitzen E.J. Brouwer (Intuitionism and Formalism [1912], p.79) | |
| A reaction: Was the turning point of Graham Priest's life the day he read this sentence? I don't agree. I take the principle of non-contradiction to be a highly generalised observation of how the world works (and Russell agrees with me). |
| 15941 | For intuitionists excluded middle is an outdated historical convention [Brouwer] |
| Full Idea: From the intuitionist standpoint the dogma of the universal validity of the principle of excluded third in mathematics can only be considered as a phenomenon of history of civilization, like the rationality of pi or rotation of the sky about the earth. | |
| From: Luitzen E.J. Brouwer (works [1930]), quoted by Shaughan Lavine - Understanding the Infinite VI.2 | |
| A reaction: [Brouwer 1952:510-11] |
| 18119 | Mathematics is a mental activity which does not use language [Brouwer, by Bostock] |
| Full Idea: Brouwer made the rather extraordinary claim that mathematics is a mental activity which uses no language. | |
| From: report of Luitzen E.J. Brouwer (Mathematics, Science and Language [1928]) by David Bostock - Philosophy of Mathematics 7.1 | |
| A reaction: Since I take language to have far less of a role in thought than is commonly believed, I don't think this idea is absurd. I would say that we don't use language much when we are talking! |
| 18247 | Brouwer saw reals as potential, not actual, and produced by a rule, or a choice [Brouwer, by Shapiro] |
| Full Idea: In his early writing, Brouwer took a real number to be a Cauchy sequence determined by a rule. Later he augmented rule-governed sequences with free-choice sequences, but even then the attitude is that Cauchy sequences are potential, not actual infinities. | |
| From: report of Luitzen E.J. Brouwer (works [1930]) by Stewart Shapiro - Philosophy of Mathematics 6.6 | |
| A reaction: This is the 'constructivist' view of numbers, as espoused by intuitionists like Brouwer. |
| 12451 | Scientific laws largely rest on the results of counting and measuring [Brouwer] |
| Full Idea: A large part of the natural laws introduced by science treat only of the mutual relations between the results of counting and measuring. | |
| From: Luitzen E.J. Brouwer (Intuitionism and Formalism [1912], p.77) | |
| A reaction: His point, I take it, is that the higher reaches of numbers have lost touch with the original point of the system. I now see the whole issue as just depending on conventions about the agreed extension of the word 'number'. |
| 18118 | Brouwer regards the application of mathematics to the world as somehow 'wicked' [Brouwer, by Bostock] |
| Full Idea: Brouwer regards as somehow 'wicked' the idea that mathematics can be applied to a non-mental subject matter, the physical world, and that it might develop in response to the needs which that application reveals. | |
| From: report of Luitzen E.J. Brouwer (Mathematics, Science and Language [1928]) by David Bostock - Philosophy of Mathematics 7.1 | |
| A reaction: The idea is that mathematics only concerns creations of the human mind. It presumably has no more application than, say, noughts-and-crosses. |
| 12454 | Intuitionists only accept denumerable sets [Brouwer] |
| Full Idea: The intuitionist recognises only the existence of denumerable sets. | |
| From: Luitzen E.J. Brouwer (Intuitionism and Formalism [1912], p.80) | |
| A reaction: That takes you up to omega, but not beyond, presumably because it then loses sight of the original intuition of 'bare two-oneness' (Idea 12453). I sympathise, but the word 'number' has shifted its meaning a lot these days. |
| 12453 | Neo-intuitionism abstracts from the reuniting of moments, to intuit bare two-oneness [Brouwer] |
| Full Idea: Neo-intuitionism sees the falling apart of moments, reunited while remaining separated in time, as the fundamental phenomenon of human intellect, passing by abstracting to mathematical thinking, the intuition of bare two-oneness. | |
| From: Luitzen E.J. Brouwer (Intuitionism and Formalism [1912], p.80) | |
| A reaction: [compressed] A famous and somewhat obscure idea. He goes on to say that this creates one and two, and all the finite ordinals. |
| 8728 | Intuitionist mathematics deduces by introspective construction, and rejects unknown truths [Brouwer] |
| Full Idea: Mathematics rigorously treated from the point of view of deducing theorems exclusively by means of introspective construction, is called intuitionistic mathematics. It deviates from classical mathematics, which believes in unknown truths. | |
| From: Luitzen E.J. Brouwer (Consciousness, Philosophy and Mathematics [1948]), quoted by Stewart Shapiro - Thinking About Mathematics 1.2 | |
| A reaction: Clearly intuitionist mathematics is a close cousin of logical positivism and the verification principle. This view would be anathema to Frege, because it is psychological. Personally I believe in the existence of unknown truths, big time! |
| 3214 | The models we use in reasoning may be more like perceptions than like language [Johnson-Laird] |
| Full Idea: The models that people use to reason are more likely to resemble perception or conception of the events (from a God's-eye view) than a string of symbols directly corresponding to the linguistic form of the premises and then applying rules of inference. | |
| From: P. Johnson-Laird (Mental Models [1983], p.53), quoted by Georges Rey - Contemporary Philosophy of Mind 10.1.2 | |
| A reaction: My intuition is that imagination is the single most important faculty in any conscious mind, and that even small animals have an inkling of the God's-eye view. Decisions need 'what-if' scenarios. |
| 10117 | Intuitonists in mathematics worried about unjustified assertion, as well as contradiction [Brouwer, by George/Velleman] |
| Full Idea: The concern of mathematical intuitionists was that the use of certain forms of inference generates, not contradiction, but unjustified assertions. | |
| From: report of Luitzen E.J. Brouwer (Intuitionism and Formalism [1912]) by A.George / D.J.Velleman - Philosophies of Mathematics Ch.6 | |
| A reaction: This seems to be the real origin of the verificationist idea in the theory of meaning. It is a hugely revolutionary idea - that ideas are not only ruled out of court by contradiction, but that there are other criteria which should also be met. |
| 7096 | We may still admire a person's character even if the traits are involuntary [Statman] |
| Full Idea: If we focus on the evaluation of character traits, voluntariness becomes less important. We would not withdraw our admiration for a person only because we found out that his or her being such a person was not a result of voluntary choice. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §3) | |
| A reaction: The need for voluntariness does not disappear. I would not admire the only generous deed you had ever performed if it was the result of hypnotism. I might admire the hypnotist. Nevertheless, I regard this idea as a crucial truth in moral theory. |
| 7098 | There is a new sort of moral scepticism, about the possibility of moral theories [Statman] |
| Full Idea: Since the 1980s, ethics has witnessed a new sort of moral scepticism, this time about the possibility of moral theories. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §4) | |
| A reaction: He cites McDowell, Williams, Nussbaum and Baier as the culprits. 'Particularism' (every situation is different, so there can't be rules) seems an essential part of virtue theory, but total absence of principles sounds to me like moral drift. |
| 7099 | With a broad concept of flourishing, it might be possible without the virtues [Statman] |
| Full Idea: In a rich conception of human flourishing, both individuals and societies seem to be able to flourish without the virtues. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §5) | |
| A reaction: I can see Aristotle clutching his head in despair at this thought. It might look like flourishing, but it couldn't be the real thing. It is Aristotle's fault, though, for including external goods. Money and pleasure offer a kind of flourishing. |
| 7100 | Virtue theory isn't a genuine ethical theory, because it doesn't have universal application [Statman] |
| Full Idea: It can be claimed that universality is a necessary property of any ethical theory and therefore virtue theory, which fails in this respect, is not a theory, and hence poses no alternative to genuine ethical theories. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §5) | |
| A reaction: Replies: a) totally universal morality is an idle dream (part of the 'Enlightenment Project' to prove everything) and we must settle for something more relative; b) virtues aren't totally universal, but they are truths about humanity. I prefer b). |
| 7102 | Promises create moral duties that have nothing to do with character [Statman] |
| Full Idea: That duties are created irrespective of facts about character is obvious from the case of promises, which bind their makers irrespective of their motives or personality. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §5) | |
| A reaction: Just occasionally a promise can be broken, by a sensitive and wise person. I promise to give your son some money; I then discover he is a drug dealer. Promises arise out of character, and cannot be made by robots. |
| 7095 | Moral education is better by concrete example than abstract principle [Statman] |
| Full Idea: According to virtue theory, education through moral exemplars is more effective than education focused on principles and obligations, because it is far more concrete. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §3) | |
| A reaction: Aristotle's view is that virtues must be developed from childhood, when principles don't mean much. The problem is that young people may witness highly virtuous behaviour in their exemplars, but totally fail to appreciate it without mention of principles. |
| 7094 | Friends express friendship even when no utility is involved [Statman] |
| Full Idea: Being a good friend means acting in ways that express the friendship even when those ways do not promote overall utility. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §3) | |
| A reaction: This implies that friendship is a true virtue of character, rather than having friends just being an 'external' good. Having friends is good; being friends is a virtue. There are duties of friendship. |
| 7104 | The ancients recognised imperfect duties, but we have added perfect duties like justice [Statman] |
| Full Idea: The advantage of modern thinkers over the ancient virtue ethicists is that in addition to imperfect duties (i.e. virtues) they also recognise the existence of perfect duties, or duties of justice, which are essential for the existence of society. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §7) | |
| A reaction: Even the Greeks had laws (e.g. Idea 422), so they understood that a society needs rules, but many laws don't seem to be moral rules (e.g. car parking), and the Greeks thought morality was about human excellence, not avoiding traffic jams. |
| 7093 | Behaviour may be disgusting or inhumane, but violate no duty [Statman] |
| Full Idea: It is surely possible, and indeed often the case, that people who violate no duty nevertheless behave in an inhumane and a disgusting manner. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §1) | |
| A reaction: This seems right, though it is easier to be disgusting than to be inhumane if no duty is to be violated. Social duties may not require a high degree of humanity, pure Kantian duties might. |
| 7103 | Abortion issues focus on the mother's right over her body, and the status of the foetus [Statman] |
| Full Idea: Most of the debate on abortion focuses on two issues, the mother's assumed right over her body, and the status of the foetus. | |
| From: Daniel Statman (Introduction to Virtue Ethics [1997], §6) | |
| A reaction: Personally I think society as a whole might have a say (if, perhaps, we are over- or under-populated, or we have a widely accepted state religion, or we are just very shocked). Mother's have virtues and duties as well as rights. |