44 ideas
| 6961 | An analogy begins to break down as soon as the two cases differ [Hume] |
| Full Idea: But wherever you depart, in the least, from the similarity of the cases, you diminish proportionably the evidence; and may at last bring it to a very weak analogy. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 2) |
| 8729 | Intuitionists deny excluded middle, because it is committed to transcendent truth or objects [Shapiro] |
| Full Idea: Intuitionists in mathematics deny excluded middle, because it is symptomatic of faith in the transcendent existence of mathematical objects and/or the truth of mathematical statements. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 1.2) | |
| A reaction: There are other problems with excluded middle, such as vagueness, but on the whole I, as a card-carrying 'realist', am committed to the law of excluded middle. |
| 8763 | The number 3 is presumably identical as a natural, an integer, a rational, a real, and complex [Shapiro] |
| Full Idea: It is surely wise to identify the positions in the natural numbers structure with their counterparts in the integer, rational, real and complex number structures. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.2) | |
| A reaction: The point is that this might be denied, since 3, 3/1, 3.00.., and -3*i^2 are all arrived at by different methods of construction. Natural 3 has a predecessor, but real 3 doesn't. I agree, intuitively, with Shapiro. Russell (1919) disagreed. |
| 18249 | Cauchy gave a formal definition of a converging sequence. [Shapiro] |
| Full Idea: A sequence a1,a2,... of rational numbers is 'Cauchy' if for each rational number ε>0 there is a natural number N such that for all natural numbers m, n, if m>N and n>N then -ε < am - an < ε. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 7.2 n4) | |
| A reaction: The sequence is 'Cauchy' if N exists. |
| 8764 | Categories are the best foundation for mathematics [Shapiro] |
| Full Idea: There is a dedicated contingent who hold that the category of 'categories' is the proper foundation for mathematics. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.3 n7) | |
| A reaction: He cites Lawvere (1966) and McLarty (1993), the latter presenting the view as a form of structuralism. I would say that the concept of a category will need further explication, and probably reduce to either sets or relations or properties. |
| 8762 | Two definitions of 3 in terms of sets disagree over whether 1 is a member of 3 [Shapiro] |
| Full Idea: Zermelo said that for each number n, its successor is the singleton of n, so 3 is {{{null}}}, and 1 is not a member of 3. Von Neumann said each number n is the set of numbers less than n, so 3 is {null,{null},{null,{null}}}, and 1 is a member of 3. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.2) | |
| A reaction: See Idea 645 - Zermelo could save Plato from the criticisms of Aristotle! These two accounts are cited by opponents of the set-theoretical account of numbers, because it seems impossible to arbitrate between them. |
| 8760 | Numbers do not exist independently; the essence of a number is its relations to other numbers [Shapiro] |
| Full Idea: The structuralist vigorously rejects any sort of ontological independence among the natural numbers; the essence of a natural number is its relations to other natural numbers. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.1) | |
| A reaction: This seems to place the emphasis on ordinals (what order?) rather than on cardinality (how many?). I am strongly inclined to think that this is the correct view, though you can't really have relations if there is nothing to relate. |
| 8761 | A 'system' is related objects; a 'pattern' or 'structure' abstracts the pure relations from them [Shapiro] |
| Full Idea: A 'system' is a collection of objects with certain relations among them; a 'pattern' or 'structure' is the abstract form of a system, highlighting the interrelationships and ignoring any features they do not affect how they relate to other objects. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.1) | |
| A reaction: Note that 'ignoring' features is a psychological account of abstraction, which (thanks to Frege and Geach) is supposed to be taboo - but which I suspect is actually indispensable in any proper account of thought and concepts. |
| 8744 | Logicism seems to be a non-starter if (as is widely held) logic has no ontology of its own [Shapiro] |
| Full Idea: The thesis that principles of arithmetic are derivable from the laws of logic runs against a now common view that logic itself has no ontology. There are no particular logical objects. From this perspective logicism is a non-starter. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 5.1) | |
| A reaction: This criticism strikes me as utterly devastating. There are two routes to go: prove that logic does have an ontology of objects (what would they be?), or - better - deny that arithmetic contains any 'objects'. Or give up logicism. |
| 8749 | Term Formalism says mathematics is just about symbols - but real numbers have no names [Shapiro] |
| Full Idea: Term Formalism is the view that mathematics is just about characters or symbols - the systems of numerals and other linguistic forms. ...This will cover integers and rational numbers, but what are real numbers supposed to be, if they lack names? | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 6.1.1) | |
| A reaction: Real numbers (such as pi and root-2) have infinite decimal expansions, so we can start naming those. We could also start giving names like 'Harry' to other reals, though it might take a while. OK, I give up. |
| 8750 | Game Formalism is just a matter of rules, like chess - but then why is it useful in science? [Shapiro] |
| Full Idea: Game Formalism likens mathematics to chess, where the 'content' of mathematics is exhausted by the rules of operating with its language. ...This, however, leaves the problem of why the mathematical games are so useful to the sciences. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 6.1.2) | |
| A reaction: This thought pushes us towards structuralism. It could still be a game, but one we learned from observing nature, which plays its own games. Chess is, after all, modelled on warfare. |
| 8752 | Deductivism says mathematics is logical consequences of uninterpreted axioms [Shapiro] |
| Full Idea: The Deductivist version of formalism (sometimes called 'if-thenism') says that the practice of mathematics consists of determining logical consequences of otherwise uninterpreted axioms. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 6.2) | |
| A reaction: [Hilbert is the source] More plausible than Term or Game Formalism (qv). It still leaves the question of why it seems applicable to nature, and why those particular axioms might be chosen. In some sense, though, it is obviously right. |
| 8753 | Critics resent the way intuitionism cripples mathematics, but it allows new important distinctions [Shapiro] |
| Full Idea: Critics commonly complain that the intuitionist restrictions cripple the mathematician. On the other hand, intuitionist mathematics allows for many potentially important distinctions not available in classical mathematics, and is often more subtle. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 7.1) | |
| A reaction: The main way in which it cripples is its restriction on talk of infinity ('Cantor's heaven'), which was resented by Hilbert. Since high-level infinities are interesting, it would be odd if we were not allowed to discuss them. |
| 8731 | Conceptualist are just realists or idealist or nominalists, depending on their view of concepts [Shapiro] |
| Full Idea: I classify conceptualists according to what they say about properties or concepts. If someone classified properties as existing independent of language I would classify her as a realist in ontology of mathematics. Or they may be idealists or nominalists. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 2.2.1) | |
| A reaction: In other words, Shapiro wants to eliminate 'conceptualist' as a useful label in philosophy of mathematics. He's probably right. All thought involves concepts, but that doesn't produce a conceptualist theory of, say, football. |
| 8730 | 'Impredicative' definitions refer to the thing being described [Shapiro] |
| Full Idea: A definition of a mathematical entity is 'impredicative' if it refers to a collection that contains the defined entity. The definition of 'least upper bound' is impredicative as it refers to upper bounds and characterizes a member of this set. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 1.2) | |
| A reaction: The big question is whether mathematics can live with impredicative definitions, or whether they threaten to be viciously circular, and undermine the whole enterprise. |
| 8725 | Rationalism tries to apply mathematical methodology to all of knowledge [Shapiro] |
| Full Idea: Rationalism is a long-standing school that can be characterized as an attempt to extend the perceived methodology of mathematics to all of knowledge. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 1.1) | |
| A reaction: Sometimes called 'Descartes's Dream', or the 'Enlightenment Project', the dream of proving everything. Within maths, Hilbert's Programme aimed for the same certainty. Idea 22 is the motto for the opposition to this approach. |
| 21285 | Events are baffling before experience, and obvious after experience [Hume] |
| Full Idea: Every event, before experience, is equally difficult and incomprehensible; and every event, after experience, is equally easy and intelligible. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 8) | |
| A reaction: If you don't believe this, spend some time watching documentaries about life in the deep oceans. Things beyond imagination swim around in front of you. But we can extrapolate, once the possibilities are revealed by experience. |
| 22330 | Grice said patterns of use are often semantically irrelevant, because it is a pragmatic matter [Grice, by Glock] |
| Full Idea: The slogan that meaning is use came under scrutiny by Grice's theory of conversational implicature. He said patterns of use shown in analysis were often semantically irrelevant, snce they are due not meanings of expressions but to pragmatic principles. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Hans-Johann Glock - What is Analytic Philosophy? 2.8 | |
| A reaction: I think the simplest objection is that words only have use because they have a meaning; The most interesting part of pragmatics is what you DON'T say in conversation. |
| 18045 | Grice's maxim of quality says do not assert what you believe to be false [Grice, by Magidor] |
| Full Idea: Grice's maxim of quality says one ought not to assert what one believes to be false. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Ofra Magidor - Category Mistakes 5.2 | |
| A reaction: The obvious exception is irony, where are truth is asserted, but the listener is supposed to spot that you are not really asserting it. |
| 18044 | Grice's maxim of manner requires one to be as brief as possible [Grice, by Magidor] |
| Full Idea: Grice's maxim of manner requires one to be as brief as possible. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Ofra Magidor - Category Mistakes 5.2 | |
| A reaction: An alternative maxim of conversation is that there should not be long silences between contributions - which would probably result if the contributions are all curtly abbreviated. |
| 18046 | Grice's maxim of quantity says be sufficiently informative [Grice, by Magidor] |
| Full Idea: Grice's maxim of quantity says 'make your contributions as informative as required'. | |
| From: report of H. Paul Grice (Some Models for Implicature [1967]) by Ofra Magidor - Category Mistakes 5.2 | |
| A reaction: Is the 'requirement' of informative for the speaker or for the listener? It is easy to image situations where, one way or the other, the two people don't agree about informativenss. |
| 6959 | We can't assume God's perfections are like our ideas or like human attributes [Hume] |
| Full Idea: But let us beware, lest we think, that our ideas anywise correspond to his perfections, or that his attributes have any resemblance to these qualities among men. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 2) |
| 6957 | The objects of theological reasoning are too big for our minds [Hume] |
| Full Idea: But in theological reasonings … we are employed upon objects, which, we must be sensible, are too large for our grasp. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 1) |
| 21255 | No being's non-existence can imply a contradiction, so its existence cannot be proved a priori [Hume] |
| Full Idea: Nothing that is distinctly conceivable implies a contradiction. Whatever we conceive of as existent we can also conceive as non-existent. So there is no being whose non-existence implies a contradiction. So no being's existence is demonstrable. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 9) | |
| A reaction: I totally subscribe to this idea, and take claims that nature actually contains contradictions (based on the inevitable quantum mechanics) to be ridiculous. Nature is the embodiment, chief exemplar and prime test of consistency. |
| 21254 | A chain of events requires a cause for the whole as well as the parts, yet the chain is just a sum of parts [Hume] |
| Full Idea: The whole chain or succession [of causes and effects], taken together, is not caused by anything, and yet it is evident that it requires a cause or reason, as much as any particular object which begins to exist in time. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 9) | |
| A reaction: This is such a major and significant idea. With blinkers on we think our questions are answered. Then someone (a philosopher, inevitably) makes you pull back and ask a much wider and more difficult question. |
| 1435 | If something must be necessary so that something exists rather than nothing, why can't the universe be necessary? [Hume] |
| Full Idea: What was it that determined something to exist rather than nothing? ...This implies a necessary being… But why may not the material universe be the necessarily existent being? | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 9) | |
| A reaction: There certainly seems no need for whatever the necessary thing is that it qualify as a 'god'. If could be a necessary subatomic particle that suddenly triggers reactions. |
| 6962 | The thing which contains order must be God, so see God where you see order [Hume] |
| Full Idea: By supposing something to contain the principle of its order within itself, we really assert it to be God; and the sooner we arrive at that divine being, so much the better. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 4) |
| 6960 | Analogy suggests that God has a very great human mind [Hume] |
| Full Idea: Since the effects resemble, we must infer by analogy that the causes also resemble; and that the Author of Nature is somewhat similar to the mind of man, though possessed of much larger faculties, proportioned to the grandeur of his work. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 2) |
| 6965 | The universe may be the result of trial-and-error [Hume] |
| Full Idea: Many worlds might have been botched and bungled, throughout an eternity, ere this system was struck out. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) |
| 6967 | Order may come from an irrational source as well as a rational one [Hume] |
| Full Idea: Why an orderly system may not be spun from the belly as well as from the brain, it will be difficult … to give a satisfactory reason. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 7) |
| 21282 | Design cannot prove a unified Deity. Many men make a city, so why not many gods for a world? [Hume] |
| Full Idea: How can you prove the unity of a Deity? A great number of men join in building a house or ship, in rearing a city; why may not several deities combine in contriving and framing a world? | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) | |
| A reaction: You might look at the Cistine Chapel ceiling and conclude that only a team could have achieve such a thing. Since there is no way to infer how many gods might be involved, then one god is a possible theory. |
| 21280 | From a ship you would judge its creator a genius, not a mere humble workman [Hume] |
| Full Idea: It is uncertain whether all the excellences of the work can justly be ascribed to the workman. If we survey a ship, what an exalted idea must we form of the ingenuity of the carpenter ...and what surprise must we feel when we find him a stupid mechanic. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) | |
| A reaction: You can at least infer that the ship was not made entirely by makers who are ignorant of carpentry. Somewhere in the divine team there must exist the skills that produce whatever we observe? |
| 21281 | This excellent world may be the result of a huge sequence of trial-and-error [Hume] |
| Full Idea: Many worlds might have been botched and bungled, throughout an eternity, ere this system was struck out; many fruitless trials made, and a slow but continued improvement carried on during infinite ages in the art of world-making. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) | |
| A reaction: Lee Smolin, a modern cosmographer, suggests that this evolution may have led to the current universe, after a long train of selective creations. The idea of natural selection was waiting to happen in 1760. |
| 21283 | Humans renew their species sexually. If there are many gods, would they not do the same? [Hume] |
| Full Idea: Men are mortal and renew their species by generation. Why must this circumstance, so universal, so essential, be excluded from those numerous and limited deities? | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) | |
| A reaction: Hume observes that this would be like the Greek gods. Hume makes mincemeat of attempts to prove the existence of God merely by analogy with human affairs. |
| 6966 | Creation is more like vegetation than human art, so it won't come from reason [Hume] |
| Full Idea: If the universe is more like animal bodies and vegetables than works of human art, it is more probable that its cause resembles the cause of the former than of the latter, and its cause should be ascribed to generation rather than to reason of design. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 7) |
| 21284 | This Creator god might be an infant or incompetent or senile [Hume] |
| Full Idea: [Maybe] this world ...was only the first essay of some infant deity ...or it is the work only of some dependent, inferior deity, the object of derision to his superiors ...or it is the product of the dotage of some superannuated deity... | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) | |
| A reaction: His opponent in the dialogue rejoices that, in the face of these sacreligious fantasies, Hume still accepts the likelihood of some sort of design. Hume is right that it is not much of a theory if nothing can be said about the Designer. |
| 21286 | Motion often begins in matter, with no sign of a controlling agent [Hume] |
| Full Idea: Motion in many instances begins in matter, without any known voluntary agent; to suppose always, in these cases, an unknown voluntary agent is mere hypothesis, attended with no advantages. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 8) | |
| A reaction: This is the modern 'powers' view of science, and a direct contradiction of Plato's claims in The Laws. It seems a bit primitive to assume that magnetism must be the work of some god. |
| 21287 | The universe could settle into superficial order, without a designer [Hume] |
| Full Idea: The universe goes on in a succession of chaos and disorder. But is it not possible that it may settle at last, so as not to lose its inherent motion and active force, yet so as to produce a uniformity of appearance, amidst the continual fluctuation. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 8) | |
| A reaction: From what I know of the constant fluctuation of virtual particles (e.g. inside protons) this is exactly what actually is happening. There is an 'appearance' of order, but at the lowest level this is not the case. |
| 21288 | Ideas arise from objects, not vice versa; ideas only influence matter if they are linked [Hume] |
| Full Idea: In all known instances, ideas are copied from real objects. You reverse this order and give thought the precedence. ...Thought has no influence upon matter except where that matter is so conjoined with it as to have an equal reciprocal influence upon it. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 8) | |
| A reaction: He allows something like mental causation, provided mind and brain are closely linked. Hume brings out the close relationship between divine design theories, and the mind-body problem. |
| 21256 | A surprise feature of all products of 9 looks like design, but is actually a necessity [Hume] |
| Full Idea: The products of 9 always compose either 9 or some lesser product of 9, if you add the characters of the product. To a superficial observer this regularity appears as chance or design, but a skilful algebraist sees it as necessity. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 9) | |
| A reaction: An example of this universal generality is that 369 is a product of 9 (9x41), and if you add 3, 6 and 9 you get 18, which is 2x9. Similar examples occur in nature, such as crystals, which are necessary once the atomic structure is known. |
| 6964 | From our limited view, we cannot tell if the universe is faulty [Hume] |
| Full Idea: It is impossible for us to tell, from our limited views, whether this system contains any great faults. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) |
| 21279 | If the divine cause is proportional to its effects, the effects are finite, so the Deity cannot be infinite [Hume] |
| Full Idea: By this method of reasoning you renounce all claim to infinity in any of the attributes of the Deity. The cause ought to be proportional to the effect, and the effect, so far as it falls under our cognizance, is not infinite. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) | |
| A reaction: You cannot deny that the Deity MAY be infinite, be only accept that your evidence is not enough to prove it. But if nothing infinite has been observed, it is a reasonable provisional inference that nothing infinite exists. |
| 6958 | How can we pronounce on a whole after a brief look at a very small part? [Hume] |
| Full Idea: A very small part of this great system, during a very short time, is very imperfectly discovered to us: and do we thence pronounce decisively concerning the origin of the whole? | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 2) |
| 6963 | Why would we infer an infinite creator from a finite creation? [Hume] |
| Full Idea: By this method of reasoning, you renounce all claim to infinity in any of the attributes of the deity. For … the cause ought only to be proportioned to the effect, and the effect, so far as it falls under our cognizance, is not infinite. | |
| From: David Hume (Dialogues Concerning Natural Religion [1751], Part 5) |