51 ideas
| 2945 | Most philosophers start with reality and then examine knowledge; Descartes put the study of knowledge first [Lehrer] |
| Full Idea: Some philosophers (e.g Plato) begin with an account of reality, and then appended an account of how we can know it, ..but Descartes turned the tables, insisting that we must first decide what we can know. | |
| From: Keith Lehrer (Theory of Knowledge (2nd edn) [2000], I p.2) |
| 2946 | You cannot demand an analysis of a concept without knowing the purpose of the analysis [Lehrer] |
| Full Idea: An analysis is always relative to some objective. It makes no sense to simply demand an analysis of goodness, knowledge, beauty or truth, without some indication of the purpose of the analysis. | |
| From: Keith Lehrer (Theory of Knowledge (2nd edn) [2000], I p.7) | |
| A reaction: Your dismantling of a car will go better if you know what a car is for, but you can still take it apart in ignorance. |
| 16512 | Semantic facts are preferable to transcendental philosophical fiction [Wiggins] |
| Full Idea: Semantical fact is almost always more interesting than transcendental philosophical fiction. | |
| From: David Wiggins (Sameness and Substance [1980], 3.1 n4) | |
| A reaction: An interesting expression of a more sophisticated recent allegiance to linguistic philosophy. There is still a strong allegiance to semantics as a major branch of philosophy, despite caution (e.g. from Nathan Salmon) about its scope. |
| 16877 | A 'constructive' (as opposed to 'analytic') definition creates a new sign [Frege] |
| Full Idea: We construct a sense out of its constituents and introduce an entirely new sign to express this sense. This may be called a 'constructive definition', but we prefer to call it a 'definition' tout court. It contrasts with an 'analytic' definition. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.210) | |
| A reaction: An analytic definition is evidently a deconstruction of a past constructive definition. Fregean definition is a creative activity. |
| 11219 | Frege suggested that mathematics should only accept stipulative definitions [Frege, by Gupta] |
| Full Idea: Frege has defended the austere view that, in mathematics at least, only stipulative definitions should be countenanced. | |
| From: report of Gottlob Frege (Logic in Mathematics [1914]) by Anil Gupta - Definitions 1.3 | |
| A reaction: This sounds intriguingly at odds with Frege's well-known platonism about numbers (as sets of equinumerous sets). It makes sense for other mathematical concepts. |
| 16878 | We must be clear about every premise and every law used in a proof [Frege] |
| Full Idea: It is so important, if we are to have a clear insight into what is going on, for us to be able to recognise the premises of every inference which occurs in a proof and the law of inference in accordance with which it takes place. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.212) | |
| A reaction: Teachers of logic like natural deduction, because it reduces everything to a few clear laws, which can be stated at each step. |
| 16867 | Logic not only proves things, but also reveals logical relations between them [Frege] |
| Full Idea: A proof does not only serve to convince us of the truth of what is proved: it also serves to reveal logical relations between truths. Hence we find in Euclid proofs of truths that appear to stand in no need of proof because they are obvious without one. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.204) | |
| A reaction: This is a key idea in Frege's philosophy, and a reason why he is the founder of modern analytic philosophy, with logic placed at the centre of the subject. I take the value of proofs to be raising questions, more than giving answers. |
| 16863 | Does some mathematical reasoning (such as mathematical induction) not belong to logic? [Frege] |
| Full Idea: Are there perhaps modes of inference peculiar to mathematics which …do not belong to logic? Here one may point to inference by mathematical induction from n to n+1. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.203) | |
| A reaction: He replies that it looks as if induction can be reduced to general laws, and those can be reduced to logic. |
| 16862 | The closest subject to logic is mathematics, which does little apart from drawing inferences [Frege] |
| Full Idea: Mathematics has closer ties with logic than does almost any other discipline; for almost the entire activity of the mathematician consists in drawing inferences. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.203) | |
| A reaction: The interesting question is who is in charge - the mathematician or the logician? |
| 16865 | 'Theorems' are both proved, and used in proofs [Frege] |
| Full Idea: Usually a truth is only called a 'theorem' when it has not merely been obtained by inference, but is used in turn as a premise for a number of inferences in the science. ….Proofs use non-theorems, which only occur in that proof. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.204) |
| 16866 | Tracing inference backwards closes in on a small set of axioms and postulates [Frege] |
| Full Idea: We can trace the chains of inference backwards, …and the circle of theorems closes in more and more. ..We must eventually come to an end by arriving at truths can cannot be inferred, …which are the axioms and postulates. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.204) | |
| A reaction: The rival (more modern) view is that that all theorems are equal in status, and axioms are selected for convenience. |
| 16868 | The essence of mathematics is the kernel of primitive truths on which it rests [Frege] |
| Full Idea: Science must endeavour to make the circle of unprovable primitive truths as small as possible, for the whole of mathematics is contained in this kernel. The essence of mathematics has to be defined by this kernel of truths. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.204-5) | |
| A reaction: [compressed] I will make use of this thought, by arguing that mathematics may be 'explained' by this kernel. |
| 16871 | A truth can be an axiom in one system and not in another [Frege] |
| Full Idea: It is possible for a truth to be an axiom in one system and not in another. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.205) | |
| A reaction: Frege aspired to one huge single system, so this is a begrudging concession, one which modern thinkers would probably take for granted. |
| 16870 | Axioms are truths which cannot be doubted, and for which no proof is needed [Frege] |
| Full Idea: The axioms are theorems, but truths for which no proof can be given in our system, and no proof is needed. It follows from this that there are no false axioms, and we cannot accept a thought as an axiom if we are in doubt about its truth. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.205) | |
| A reaction: He struggles to be as objective as possible, but has to concede that whether we can 'doubt' the axiom is one of the criteria. |
| 16869 | To create order in mathematics we need a full system, guided by patterns of inference [Frege] |
| Full Idea: We cannot long remain content with the present fragmentation [of mathematics]. Order can be created only by a system. But to construct a system it is necessary that in any step forward we take we should be aware of the logical inferences involved. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.205) |
| 17529 | Maybe the concept needed under which things coincide must also yield a principle of counting [Wiggins] |
| Full Idea: My thesis C says that to specify something or other under which a and b coincide is to specify a concept f which qualifies for this purpose only if it yields a principle of counting for fs. ...I submit that C is false, though a near miss. | |
| From: David Wiggins (Sameness and Substance [1980], 1.1) |
| 17530 | The sortal needed for identities may not always be sufficient to support counting [Wiggins] |
| Full Idea: My principle C seems unnecessary ...since it is one thing to see how many fs there are...but another to have a perfectly general method. ...One could answer whether this f-compliant is the same as that one, but there are too many ways to articulate it. | |
| From: David Wiggins (Sameness and Substance [1980], 2.8) | |
| A reaction: His famous example is trying to count the Pope's crown, which is made of crowns. A clearer example might be a rectangular figure divided up into various overlapping rectangles. Individuation is easy, but counting is contextual. |
| 16864 | If principles are provable, they are theorems; if not, they are axioms [Frege] |
| Full Idea: If the law [of induction] can be proved, it will be included amongst the theorems of mathematics; if it cannot, it will be included amongst the axioms. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.203) | |
| A reaction: This links Frege with the traditional Euclidean view of axioms. The question, then, is how do we know them, given that we can't prove them. |
| 16523 | Realist Conceptualists accept that our interests affect our concepts [Wiggins] |
| Full Idea: The realist conceptualist may cheerfully admit that the sortal concepts of which we are possessed are the creatures of our interests; …and also that there need be no one way in which we must articulate reality. | |
| From: David Wiggins (Sameness and Substance [1980], 5.2) | |
| A reaction: Wiggins calls himself a 'realist conceptualist'. In his terminology, I seem to be an 'anti-conceptualist realist'. The issue concerns aspects of reality that extend beyond our concepts. The 99th d.p. of the mass of the electron. |
| 16524 | Conceptualism says we must use our individuating concepts to grasp reality [Wiggins] |
| Full Idea: What Conceptualism entails is that, although horses and stars are not inventions or artefacts, in order to single out these things we must deploy a conceptual scheme which has been formed in such a way as to make singling them out possible. | |
| From: David Wiggins (Sameness and Substance [1980], 5.5) | |
| A reaction: I don't quite see why the 'singling out' role of the concepts is the only one that generates them, or makes them fit for purpose. In general, of course, our conceptual scheme is necessarily a response to our experience of the world. |
| 16526 | Animal classifications: the Emperor's, fabulous, innumerable, like flies, stray dogs, embalmed…. [Wiggins] |
| Full Idea: A Chinese encyclopedia classifies animals as belonging to the Emperor, embalmed, tame, sucking pigs, sirens, fabulous, stray dogs, included in this classification, frenzied, innumerable, drawn with a fine brush, etcetera, or look for afar like flies. | |
| From: David Wiggins (Sameness and Substance [1980], 5.7 n18) | |
| A reaction: [This glorious quotation comes from a story by Borges, first spotted by Foucault] |
| 16492 | Individuation needs accounts of identity, of change, and of singling out [Wiggins] |
| Full Idea: A theory of individuation must comprise at least three things: an elucidation of the primitive concept of identity or sameness; what it is to be a substance that persists through change; and what it is for a thinker to single out the same substance. | |
| From: David Wiggins (Sameness and Substance [1980], Pre 1) | |
| A reaction: [compressed] Metaphysics seems to need a theory of identity, but I am not yet convinced that it also needs a theory of 'individuation'. Never mind, press on and create one, and see how it looks. Aristotle wanted to explain predication too. |
| 16493 | Individuation can only be understood by the relation between things and thinkers [Wiggins] |
| Full Idea: Understanding the concepts involved in individuation can only be characterised by reference to observable commerce between things singled out and thinkers who think or find their way around the world precisely by singling them out. | |
| From: David Wiggins (Sameness and Substance [1980], Pre 1) | |
| A reaction: I take individuation to be relatively uninteresting, because I understand identity independently of how we single things out, but Wiggins's reliance on sortals implies that the very identity of things in the world is knee deep in mental activity. |
| 16496 | Singling out extends back and forward in time [Wiggins] |
| Full Idea: The singling out of a substance at a time reaches backwards and forwards to time before and after that time. | |
| From: David Wiggins (Sameness and Substance [1980], Pre 2) | |
| A reaction: Presumably this is an inferred history and persistence conditions. Sounds fine in a stable world. We assume (a priori?) that any object will have a space-time line for its duration. |
| 16495 | The only singling out is singling out 'as' something [Wiggins] |
| Full Idea: There could be no singling out tout court unless there could be singling out 'as'. | |
| From: David Wiggins (Sameness and Substance [1980], Pre 2) | |
| A reaction: I find this claim baffling. Do animals categorise everything they engage with? Are we unable to engage with something if we have not yet categorised it? Surely picking it out is prior to saying that sort of thing it is? |
| 16501 | In Aristotle's sense, saying x falls under f is to say what x is [Wiggins] |
| Full Idea: To say that x falls under f - or that x is an f - is to say what x is (in the sense Aristotle isolated). | |
| From: David Wiggins (Sameness and Substance [1980], 2.1) | |
| A reaction: This is a key claim in Wiggins's main principle. I'm not convinced. He wants one main sortal to do all the work. I don't think Aristotle at all intended the 'nature' of an individual thing to be given by a single sortal under which it falls. |
| 16506 | Every determinate thing falls under a sortal, which fixes its persistence [Wiggins] |
| Full Idea: We can expect that, for every completely determinate continuant, there will be at least one sortal concept that it falls under and that determines a principle of persistence for it. | |
| From: David Wiggins (Sameness and Substance [1980], 2.4) | |
| A reaction: I think he has the 'determines' relation the wrong way round! Being a tiger doesn't determine anything about persistence. It is having that nature and those persistence conditions which make it a tiger. And why does he optimistically 'expect' this? |
| 9388 | Every concept must have a sharp boundary; we cannot allow an indeterminate third case [Frege] |
| Full Idea: Of any concept, we must require that it have a sharp boundary. Of any object it must hold either that it falls under the concept or it does not. We may not allow a third case in which it is somehow indeterminate whether an object falls under a concept. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.229), quoted by Ian Rumfitt - The Logic of Boundaryless Concepts p.1 n1 | |
| A reaction: This is the voice of the classical logician, which has echoed by Russell. I'm with them, I think, in the sense that logic can only work with precise concepts. The jury is still out. Maybe we can 'precisify', without achieving total precision. |
| 16509 | Natural kinds are well suited to be the sortals which fix substances [Wiggins] |
| Full Idea: Among the best candidates to play the roles of sortal and substantial predicates are the natural kind words. | |
| From: David Wiggins (Sameness and Substance [1980], 3.1) | |
| A reaction: There is always a danger of circularity with this kind of approach. How do we distinguish the genuine natural kinds from the dubious ones? |
| 16514 | Artefacts are individuated by some matter having a certain function [Wiggins] |
| Full Idea: Ordinary artefacts are individuated, rather indeterminately and arbitrarily, by reference to a parcel of matter so organised as to subserve a certain function. | |
| From: David Wiggins (Sameness and Substance [1980], 3.3) |
| 16510 | Nominal essences don't fix membership, ignore evolution, and aren't contextual [Wiggins] |
| Full Idea: Nominal essences are unsatisfactory because they fail either of necessity or of sufficiency for membership of the intended kind, they leave unexplained how sortals can evolve, and there is no room for culture or context in our reference to kinds. | |
| From: David Wiggins (Sameness and Substance [1980], 3.1) | |
| A reaction: [a compression of a paragraph] I would have thought that Locke would just say it is tough luck if nominal essences can't do all these things, because that's just the way it is, folks. |
| 16503 | 'What is it?' gives the kind, nature, persistence conditions and identity over time of a thing [Wiggins] |
| Full Idea: The question 'what is it?' refers to the persistence and lifespan of an entity, and so manifests the identity over time of an entity and its persistence, between persistence and existence, and between its existence and being the kind of thing it is. | |
| From: David Wiggins (Sameness and Substance [1980], 2.1) | |
| A reaction: The idea that establishing the kind of a thing can do all this work strikes me as false. The lifespan of a 'human' can be between five minutes and a hundred years. Humans have a clear death, but thunderstorms don't. |
| 16499 | A restored church is the same 'church', but not the same 'building' or 'brickwork' [Wiggins] |
| Full Idea: We can say of Hume's church that the present church is the same 'church' as the old parish church but not the same 'building' or the same 'stonework' as the old parish church. | |
| From: David Wiggins (Sameness and Substance [1980], 1.5) | |
| A reaction: Unconvinced. This seems to make a 'church' into an abstraction, which might even exist in the absence of any building. And it seems to identify a building with its stonework. Wiggins yearns for a neat solution, but it ain't here. |
| 16515 | A thing begins only once; for a clock, it is when its making is first completed [Wiggins] |
| Full Idea: A thing starts existing only once; and in the case of a clock its proper beginning was at about the time when its maker finished it. | |
| From: David Wiggins (Sameness and Substance [1980], 3.3) | |
| A reaction: I love the example that challenges this. Take the clock's parts and use them to make other clocks, then collect them up and reassemble the first clock. If the first clock has persisted through this, you have too many clocks. Wiggins spots some of this. |
| 16517 | Priests prefer the working ship; antiquarians prefer the reconstruction [Wiggins] |
| Full Idea: Dispute might break out between priests who favoured the working ship and antiquarians who preferred the reconstruction. | |
| From: David Wiggins (Sameness and Substance [1980], 3.3) | |
| A reaction: This captures the contextual nature of the dispute very succinctly. Wiggins, of course, thinks that sortals will settle the matter. Fat chance. |
| 16498 | Identity cannot be defined, because definitions are identities [Wiggins] |
| Full Idea: Since any definition is an identity, identity itself cannot be defined. | |
| From: David Wiggins (Sameness and Substance [1980], 1.2 n7) | |
| A reaction: This sounds too good to be true! I can't think of an objection, so, okay, identity cannot possibly be defined. We can give synonyms for it, I suppose. [Wrong, says Rumfitt! Definitions can also be equivalences!] |
| 16497 | Leibniz's Law (not transitivity, symmetry, reflexivity) marks what is peculiar to identity [Wiggins] |
| Full Idea: The principle of Leibniz's Law marks off what is peculiar to identity and differentiates it in a way in which transitivity, symmetry and reflexivity (all shared by 'exact similarity, 'equality in pay', etc.) do not. | |
| From: David Wiggins (Sameness and Substance [1980], 1.2) |
| 16502 | Identity is primitive [Wiggins] |
| Full Idea: Identity is a primitive notion. | |
| From: David Wiggins (Sameness and Substance [1980], 2.1) | |
| A reaction: To be a true primitive it would have to be univocal, but it seems to me that 'identity' comes in degrees. The primitive concept is the minimal end of the degrees, but there are also more substantial notions of identity. |
| 16521 | A is necessarily A, so if B is A, then B is also necessarily A [Wiggins] |
| Full Idea: The famous proof of Barcan Marcus about necessity of identity comes down to simply this: Hesperus is necessarily Hesperus, so if Phosphorus is Hesperus, Phosphorus is necessarily Hesperus. | |
| From: David Wiggins (Sameness and Substance [1980], 4.3) | |
| A reaction: Since the identity of Hesperus and Phosphorus was an a posteriori discovery, this was taken to be the inception of the idea that there are a posteriori necessities. The conclusion seems obvious. One thing is necessarily one thing. |
| 16505 | By the principle of Indiscernibility, a symmetrical object could only be half of itself! [Wiggins] |
| Full Idea: The full Identity of Indiscernibles excludes the existence in this world of a symmetrical object, which is reduced to half of itself by the principle. If symmetrical about all planes that bisect it, it is precluded altogether from existence. | |
| From: David Wiggins (Sameness and Substance [1980], 2.2) | |
| A reaction: A really nice objection. Do the parts even need to be symmetrical? My eyeballs can't be identical to one another, presumably. Electrons already gave the principle big trouble. |
| 16494 | We want to explain sameness as coincidence of substance, not as anything qualitative [Wiggins] |
| Full Idea: The notion of sameness or identity that we are to elucidate is not that of any degree of qualitative similarity but of coincidence as a substance - a notion as primitive as predication. | |
| From: David Wiggins (Sameness and Substance [1980], Pre 2) | |
| A reaction: This question invites an approach to identity through our descriptions of it, rather than to the thing itself. There is no problem in ontology of two substances being 'the same', because they are just one substance. |
| 16522 | It is hard or impossible to think of Caesar as not human [Wiggins] |
| Full Idea: It is hard or impossible to conceive of Caesar's not being a man (human). | |
| From: David Wiggins (Sameness and Substance [1980], 4.5) | |
| A reaction: So is it 'hard' or is it 'impossible'? Older generations of philosophers simply didn't read enough science fiction. Any short story could feature Caesar's failure to be a man. His assassination was a disaster for the Martian invasion of 44 BCE. |
| 16525 | Our sortal concepts fix what we find in experience [Wiggins] |
| Full Idea: What sortal concepts we can bring to bear upon experience determines what we can find there. | |
| From: David Wiggins (Sameness and Substance [1980], 5.6) | |
| A reaction: Wiggins would wince at being classed among linguistic relativists of the Sapir-Whorf type, but that's where I'm putting this idea. Wiggins is a realist, who knows there are things out there our concepts miss. He compares it to a fishing net. He's wrong. |
| 16876 | We need definitions to cram retrievable sense into a signed receptacle [Frege] |
| Full Idea: If we need such signs, we also need definitions so that we can cram this sense into the receptacle and also take it out again. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.209) | |
| A reaction: Has anyone noticed that Frege is the originator of the idea of the mental file? Has anyone noticed the role that definition plays in his account? |
| 16875 | We use signs to mark receptacles for complex senses [Frege] |
| Full Idea: We often need to use a sign with which we associate a very complex sense. Such a sign seems a receptacle for the sense, so that we can carry it with us, while being always aware that we can open this receptacle should we need what it contains. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.209) | |
| A reaction: This exactly the concept of a mental file, which I enthusiastically endorse. Frege even talks of 'opening the receptacle'. For Frege a definition (which he has been discussing) is the assigment of a label (the 'definiendum') to the file (the 'definiens'). |
| 16518 | We conceptualise objects, but they impinge on us [Wiggins] |
| Full Idea: The mind conceptualises objects, yet objects impinge upon the mind. | |
| From: David Wiggins (Sameness and Substance [1980], 3.5) | |
| A reaction: A very nice statement of the relationship, and the fact that we don't just make our concepts up. |
| 16511 | A 'conception' of a horse is a full theory of what it is (and not just the 'concept') [Wiggins] |
| Full Idea: A 'conception' of horse is a theory of what a horse is, or what it is to be a horse. The conception is in no way the same as the concept. The conception is of the concept. | |
| From: David Wiggins (Sameness and Substance [1980], 3.1) | |
| A reaction: Wiggins sounds confident about a sharp distinction here, which I doubt, but some such distinction seems to required. I quite like Williams's 'fat' and 'thin' concepts. |
| 16879 | A sign won't gain sense just from being used in sentences with familiar components [Frege] |
| Full Idea: No sense accrues to a sign by the mere fact that it is used in one or more sentences, the other constituents of which are known. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.213) | |
| A reaction: Music to my ears. I've never grasped how meaning could be grasped entirely through use. |
| 16873 | Thoughts are not subjective or psychological, because some thoughts are the same for us all [Frege] |
| Full Idea: A thought is not something subjective, is not the product of any form of mental activity; for the thought that we have in Pythagoras's theorem is the same for everybody. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.206) | |
| A reaction: When such thoughts are treated as if the have objective (platonic) existence, I become bewildered. I take a thought (or proposition) to be entirely psychological, but that doesn't stop two people from having the same thought. |
| 16872 | A thought is the sense expressed by a sentence, and is what we prove [Frege] |
| Full Idea: The sentence is of value to us because of the sense that we grasp in it, which is recognisably the same in a translation. I call this sense the thought. What we prove is not a sentence, but a thought. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.206) | |
| A reaction: The 'sense' is presumably the German 'sinn', and a 'thought' in Frege is what we normally call a 'proposition'. So the sense of a sentence is a proposition, and logic proves propositions. I'm happy with that. |
| 16874 | The parts of a thought map onto the parts of a sentence [Frege] |
| Full Idea: A sentence is generally a complex sign, so the thought expressed by it is complex too: in fact it is put together in such a way that parts of a thought correspond to parts of the sentence. | |
| From: Gottlob Frege (Logic in Mathematics [1914], p.207) | |
| A reaction: This is the compositional view of propositions, as opposed to the holistic view. |