37 ideas
| 22496 | Wisdom only implies the knowledge achievable in any normal lifetime [Foot] |
| Full Idea: Wisdom implies no more knowledge and understanding than anyone of normal capacity can and should acquire in the course of an ordinary life. | |
| From: Philippa Foot (Natural Goodness [2001], 5) | |
| A reaction: Have philosophers stopped talking about wisdom precisely because you now need three university degrees to be considered even remotely good at phillosophy? Hence wisdom is an inferior attainment, because Foot is right. |
| 17926 | Rejecting double negation elimination undermines reductio proofs [Colyvan] |
| Full Idea: The intuitionist rejection of double negation elimination undermines the important reductio ad absurdum proof in classical mathematics. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) |
| 17925 | Showing a disproof is impossible is not a proof, so don't eliminate double negation [Colyvan] |
| Full Idea: In intuitionist logic double negation elimination fails. After all, proving that there is no proof that there can't be a proof of S is not the same thing as having a proof of S. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) | |
| A reaction: I do like people like Colyvan who explain things clearly. All of this difficult stuff is understandable, if only someone makes the effort to explain it properly. |
| 17924 | Excluded middle says P or not-P; bivalence says P is either true or false [Colyvan] |
| Full Idea: The law of excluded middle (for every proposition P, either P or not-P) must be carefully distinguished from its semantic counterpart bivalence, that every proposition is either true or false. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) | |
| A reaction: So excluded middle makes no reference to the actual truth or falsity of P. It merely says P excludes not-P, and vice versa. |
| 17929 | Löwenheim proved his result for a first-order sentence, and Skolem generalised it [Colyvan] |
| Full Idea: Löwenheim proved that if a first-order sentence has a model at all, it has a countable model. ...Skolem generalised this result to systems of first-order sentences. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 2.1.2) |
| 17930 | Axioms are 'categorical' if all of their models are isomorphic [Colyvan] |
| Full Idea: A set of axioms is said to be 'categorical' if all models of the axioms in question are isomorphic. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 2.1.2) | |
| A reaction: The best example is the Peano Axioms, which are 'true up to isomorphism'. Set theory axioms are only 'quasi-isomorphic'. |
| 17928 | Ordinal numbers represent order relations [Colyvan] |
| Full Idea: Ordinal numbers represent order relations. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.2.3 n17) |
| 17923 | Intuitionists only accept a few safe infinities [Colyvan] |
| Full Idea: For intuitionists, all but the smallest, most well-behaved infinities are rejected. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) | |
| A reaction: The intuitionist idea is to only accept what can be clearly constructed or proved. |
| 17941 | Infinitesimals were sometimes zero, and sometimes close to zero [Colyvan] |
| Full Idea: The problem with infinitesimals is that in some places they behaved like real numbers close to zero but in other places they behaved like zero. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 7.1.2) | |
| A reaction: Colyvan gives an example, of differentiating a polynomial. |
| 17922 | Reducing real numbers to rationals suggested arithmetic as the foundation of maths [Colyvan] |
| Full Idea: Given Dedekind's reduction of real numbers to sequences of rational numbers, and other known reductions in mathematics, it was tempting to see basic arithmetic as the foundation of mathematics. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.1) | |
| A reaction: The reduction is the famous Dedekind 'cut'. Nowadays theorists seem to be more abstract (Category Theory, for example) instead of reductionist. |
| 17936 | Transfinite induction moves from all cases, up to the limit ordinal [Colyvan] |
| Full Idea: Transfinite inductions are inductive proofs that include an extra step to show that if the statement holds for all cases less than some limit ordinal, the statement also holds for the limit ordinal. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1 n11) |
| 17940 | Most mathematical proofs are using set theory, but without saying so [Colyvan] |
| Full Idea: Most mathematical proofs, outside of set theory, do not explicitly state the set theory being employed. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 7.1.1) |
| 17931 | Structuralism say only 'up to isomorphism' matters because that is all there is to it [Colyvan] |
| Full Idea: Structuralism is able to explain why mathematicians are typically only interested in describing the objects they study up to isomorphism - for that is all there is to describe. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 3.1.2) |
| 17932 | If 'in re' structures relies on the world, does the world contain rich enough structures? [Colyvan] |
| Full Idea: In re structuralism does not posit anything other than the kinds of structures that are in fact found in the world. ...The problem is that the world may not provide rich enough structures for the mathematics. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 3.1.2) | |
| A reaction: You can perceive a repeating pattern in the world, without any interest in how far the repetitions extend. |
| 17943 | Probability supports Bayesianism better as degrees of belief than as ratios of frequencies [Colyvan] |
| Full Idea: Those who see probabilities as ratios of frequencies can't use Bayes's Theorem if there is no objective prior probability. Those who accept prior probabilities tend to opt for a subjectivist account, where probabilities are degrees of belief. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 9.1.8) | |
| A reaction: [compressed] |
| 17939 | Mathematics can reveal structural similarities in diverse systems [Colyvan] |
| Full Idea: Mathematics can demonstrate structural similarities between systems (e.g. missing population periods and the gaps in the rings of Saturn). | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 6.3.2) | |
| A reaction: [Colyvan expounds the details of his two examples] It is these sorts of results that get people enthusiastic about the mathematics embedded in nature. A misunderstanding, I think. |
| 17938 | Mathematics can show why some surprising events have to occur [Colyvan] |
| Full Idea: Mathematics can show that under a broad range of conditions, something initially surprising must occur (e.g. the hexagonal structure of honeycomb). | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 6.3.2) |
| 17934 | Proof by cases (by 'exhaustion') is said to be unexplanatory [Colyvan] |
| Full Idea: Another style of proof often cited as unexplanatory are brute-force methods such as proof by cases (or proof by exhaustion). | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1) |
| 17933 | Reductio proofs do not seem to be very explanatory [Colyvan] |
| Full Idea: One kind of proof that is thought to be unexplanatory is the 'reductio' proof. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1) | |
| A reaction: Presumably you generate a contradiction, but are given no indication of why the contradiction has arisen? Tracking back might reveal the source of the problem? Colyvan thinks reductio can be explanatory. |
| 17935 | If inductive proofs hold because of the structure of natural numbers, they may explain theorems [Colyvan] |
| Full Idea: It might be argued that any proof by induction is revealing the explanation of the theorem, namely, that it holds by virtue of the structure of the natural numbers. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1) | |
| A reaction: This is because induction characterises the natural numbers, in the Peano Axioms. |
| 17942 | Can a proof that no one understands (of the four-colour theorem) really be a proof? [Colyvan] |
| Full Idea: The proof of the four-colour theorem raises questions about whether a 'proof' that no one understands is a proof. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 9.1.6) | |
| A reaction: The point is that the theorem (that you can colour countries on a map with just four colours) was proved with the help of a computer. |
| 17937 | Mathematical generalisation is by extending a system, or by abstracting away from it [Colyvan] |
| Full Idea: One type of generalisation in mathematics extends a system to go beyond what is was originally set up for; another kind involves abstracting away from some details in order to capture similarities between different systems. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.2) |
| 23694 | All criterions of practical rationality derive from goodness of will [Foot] |
| Full Idea: I want to say, baldly, that there is no criterion for practical rationality that is not derived from that of goodness of will. | |
| From: Philippa Foot (Natural Goodness [2001], 1) | |
| A reaction: Where does that put the successful and clever criminal? Presumably they are broadly irrational, but narrowly rational - but that is not very clear distinction. She says Kant's concept of the good will is too pure, and unrelated to human good. |
| 23686 | Moral reason is not just neutral, because morality is part of the standard of rationality [Foot, by Hacker-Wright] |
| Full Idea: In her late period she again reverses her thoughts on moral rationalism; …rather than a neutral rationality which fulfils desires, she argues that morality ought to be thought of as part of the standard of rationality itself. | |
| From: report of Philippa Foot (Natural Goodness [2001]) by John Hacker-Wright - Philippa Foot's Moral Thought Intro | |
| A reaction: This comes much closer to the Greek and Aristotelian concept of logos. They saw morality as inseparable from our judgements about how the world is. All 'sensible' thinking will involve what is good for humanity. |
| 23693 | Practical rationality must weigh both what is morally and what is non-morally required [Foot] |
| Full Idea: Different considerations are on a par, in that judgement about what is required by practical rationality must take account of their interaction: of the weight of the ones we call non-moral as well as those we call moral. | |
| From: Philippa Foot (Natural Goodness [2001], 1) | |
| A reaction: Her final settled view of rationalism in morality, it seems. The point is that moral considerations are not paramount, because she sees possible justifications for ignoring moral rules (like 'don't lie') in certain practical situations. |
| 23687 | Moral virtues arise from human nature, as part of what makes us good human beings [Foot, by Hacker-Wright] |
| Full Idea: In her later work she offers a view of the relationship of morality to human nature, arguing that the moral virtues are part of what makes us good as human beings. | |
| From: report of Philippa Foot (Natural Goodness [2001]) by John Hacker-Wright - Philippa Foot's Moral Thought Intro | |
| A reaction: In this phase she talks explicitly of the Aristotelian idea that successful function is the grounding of what is good for any living being, including humans. |
| 22493 | Sterility is a human defect, but the choice to be childless is not [Foot] |
| Full Idea: Lack of capacity to reproduce is a defect in a human being. But choice of childlessness and even celibacy is not thereby shown to be defective choice, because human good is not the same as plant or animal good. | |
| From: Philippa Foot (Natural Goodness [2001], 3) | |
| A reaction: Is failure to reproduce a defect in an animal? If goodness and virtue derive from function, it is hard to see how deliberate childlessness could be a human good, even if it is not a defect. Choosing to terminate a hereditary defect seems good. |
| 22492 | Virtues are as necessary to humans as stings are to bees [Foot] |
| Full Idea: Virtues play a necessary part in the life of human beings as do stings in the life of a bee. | |
| From: Philippa Foot (Natural Goodness [2001], 2) | |
| A reaction: This presumably rests on the Aristotelian idea that humans are essentially social (as opposed to solitary humans who choose to be social, perhaps in a contractual way, as Plato implies). |
| 22491 | Moral evaluations are not separate from facts, but concern particular facts about functioning [Foot] |
| Full Idea: A moral evaluation does not stand over against the statement of a matter of fact, but rather has to do with facts about a particular subject matter, as do evaluations of such things as sight and hearing in animals. | |
| From: Philippa Foot (Natural Goodness [2001], 1) | |
| A reaction: She avoids the word 'function', and only deals with living creatures, but she uses a 'good knife' as an example, and this Aristotelian view clearly applies to any machine which has a function. |
| 22497 | Deep happiness usually comes from the basic things in life [Foot] |
| Full Idea: Possible objects of deep happiness seem to be things that are basic in human life, such as home, and family, and work, and friendship. | |
| From: Philippa Foot (Natural Goodness [2001], 6) | |
| A reaction: I've not encountered discussion of 'deep' happiness before. I heard of an old man in tears because he had just seen a Purple Emperor butterfly for the first time. She makes it sound very conservative. How about mountaineering achievements? |
| 22498 | Happiness is enjoying the pursuit and attainment of right ends [Foot] |
| Full Idea: In my terminology 'happiness' is understood as the enjoyment of good things, meaning the enjoyment in attaining, and in pursuing, right ends. | |
| From: Philippa Foot (Natural Goodness [2001], 6) | |
| A reaction: A modified version of Aristotle's view, which she contrasts with McDowell's identification of happiness with the life of virtue. They all seem to have an optimistic hope that the pleasure in being a bit wicked is false happiness. |
| 23695 | Good actions can never be justified by the good they brings to their agent [Foot] |
| Full Idea: There is no good case for assessing the goodness of human action by reference only to good that each person brings to himself. | |
| From: Philippa Foot (Natural Goodness [2001], 1) | |
| A reaction: She observes that even non-human animals often act for non-selfish reasons. The significance of this is its rejection of her much earlier view that virtues are justified by the good they bring their possessor. |
| 22499 | We all know that just pretending to be someone's friend is not the good life [Foot] |
| Full Idea: We know perfectly well that it is not true that the best life would consist in successfully pretending friendship: having friends to serve one but without being a real friend oneself. | |
| From: Philippa Foot (Natural Goodness [2001], 7) | |
| A reaction: For some skallywags the achieving of something for nothing seems to be very much the good life, but not many of them want to exploit people who are seen to be their friends. |
| 22495 | Someone is a good person because of their rational will, not their body or memory [Foot] |
| Full Idea: To speak of a good person is to speak of an individual not in respect of his body, or of faculties such as sight and memory, but as concerns his rational will (his 'will as controllable by reason'). | |
| From: Philippa Foot (Natural Goodness [2001], 5) | |
| A reaction: She more or less agrees with Kant that the only truly good moral thing is a good will, though she has plenty of other criticisms of his views. |
| 22502 | Refraining from murder is not made good by authenticity or self-fulfilment [Foot] |
| Full Idea: If a stranger should come on us when we are sleeping he will not think it all right to kill us. …In human life as it is, this kind of action is not made good by authenticity or self-fulfilment in the one who does it. | |
| From: Philippa Foot (Natural Goodness [2001], 7) | |
| A reaction: A rare swipe from Foot at existentialism, which she hardly ever mentions. I find it hard to see these existential virtues as in any way moral. It means nothing to other citizens whether one of their number is 'authentic'. |
| 21997 | In Marxism the state will be superseded [Singer] |
| Full Idea: It is a famous Marxist doctrine that the state will be superseded. | |
| From: Peter Singer (Marx [1980], 9) | |
| A reaction: Why is that final state communism rather than anarchism? |
| 21993 | Materialist history says we are subject to incomprehensible forces [Singer] |
| Full Idea: The materialist conception of history tells us that human beings are totally subject to forces they do not understand and control. | |
| From: Peter Singer (Marx [1980], 6) | |
| A reaction: How does Marx know the forces? An exceptionally influential idea, because it is a modern commonplace that we have very little control over our own lives (apart from right wingers asserting that 'you can have anything if you really really want it'). |