89 ideas
| 18877 | Moral realism doesn't seem to entail the existence of any things [Cameron] |
| Full Idea: Moral realism isn't realism about things, and it seems strange to suggest that moral realism is existence entailing in the way that realism about unobservable is. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Realism') | |
| A reaction: Cameron is questioning whether a realist has to believe in truthmakers. It seems to me that his doubts are because he insists that truthmaking is committed to the existence of 'things'. I assume any moral realism must supervene on nature. |
| 18868 | Surely if some propositions are grounded in existence, they all are? [Cameron] |
| Full Idea: What possible reason could one have for thinking of some propositions that they need to be grounded in what there is that doesn't apply to all propositions? | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Max and Nec') | |
| A reaction: Well, if truthmaking said that all truths are grounded, then some could be grounded in what there is, and others in how it is, or maybe even how it isn't (if you get a decent account of negative truths). |
| 18928 | If maximalism is necessary, then that nothing exists has a truthmaker, which it can't have [Cameron] |
| Full Idea: I think truthmaker theory is contingently true. [n24] If there could have been nothing, what makes that true? But if truthmaker maximalism is a necessary truth, there's necessarily something. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 4 n24) | |
| A reaction: Truthmaking is beginning to feel like Gödel's Theorems. You can 'make' lots and lots of truths ('prove' in Gödel), but there will be truths that elude the making. Truthmaker theory itself will be one example. So is Maximalism another one? |
| 18867 | Orthodox Truthmaker applies to all propositions, and necessitates their truth [Cameron] |
| Full Idea: Orthodox truthmaker theory (Armstrong's) entails Maximalism (that every true proposition has at least one truthmaker), and Necessitarianism (that the existence of a truthmaker necessitates the truth of its proposition). | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Max and Nec') | |
| A reaction: I think I accept both of these. If you say only some truths have truthmakers, the other truths are then baffling. And how could a truthmaker fail in its job? But that doesn't necessitate the existence of the proposition. |
| 18873 | God fixes all the truths of the world by fixing what exists [Cameron] |
| Full Idea: The truthmaker thought is that explanation only bottoms out at existence facts; for God to give a complete plan of the world He needs only make an inventory of what is to exist. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Max and Nec') | |
| A reaction: He is defending Necessitarianism about truthmaking. I'm struggling with this. An inventory of the contents of my house doesn't begin to fix all the truths that arise from them. Why is Cameron so resistent to 'how' things are being part of the truthmaking? |
| 15395 | Give up objects necessitating truths, and say their natures cause the truths? [Cameron] |
| Full Idea: We could abandon the view that truthmakers necessitate the truth of that which makes them true, and say that an object makes a truth when its intrinsic nature suffices for that truth. The object would have a different intrinsic nature if the truth failed. | |
| From: Ross P. Cameron (Intrinsic and Extrinsic Properties [2009], 'Truthmakers') | |
| A reaction: [He cites Josh Parsons 1999, 2005 for this] This approach seems closely related to Kit Fine's proposal that necessities arise from the natures of things. It sounds to me as if an object with that intrinsic nature would necessitate that truth. |
| 18931 | Determinate truths don't need extra truthmakers, just truthmakers that are themselves determinate [Cameron] |
| Full Idea: I reject saying there must be an additional truthmaker for 'Determinately, p': rather, I say that the truthmaker for p must simply be a determinate existent rather than a mere existent. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 6) | |
| A reaction: As he puts it (quite persuasively), God doesn't need to add an extra truthmaker for a determinate truth. Cameron rejects Necessitarianism. He uses 'determinate' fairly uncritically. What makes the truth of the truthmaker's determinacy? |
| 18879 | What the proposition says may not be its truthmaker [Cameron] |
| Full Idea: The explanation of the truth of the proposition [p] doesn't stop at it being the case that p, so it's false to claim that whenever a proposition is true it's true in virtue of the world being as the proposition says it is. The features often lie deeper. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Grounding') | |
| A reaction: [He is opposing Jennifer Hornsby 2005] Cameron offers 'the average family has 2.4 children' as a counterexample' (since no one actually has 2.4 children). That seems compelling. Second example: 'the rose is beautiful'. |
| 18880 | Rather than what exists, some claim that the truthmakers are ways of existence, dispositions, modalities etc [Cameron] |
| Full Idea: Rivals to the truthmaker claim that facts about what there is are the truthmakers, there are theories that add facts about how the things are, or add dispositional facts, or modal facts, or haecceitistic facts, or maybe moral facts. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Grounding') | |
| A reaction: [compressed] He seems to think his version has a monopoly on truthmaking, but I don't see why these other theories shouldn't count as truthmaking. The truthmaker for 'live grenades are dangerous' is not just the existence of grenades. |
| 18874 | Truthmaking doesn't require realism, because we can be anti-realist about truthmakers [Cameron] |
| Full Idea: It's definitely not sufficient to be a realist that one be a truthmaker theorist, since one can simply be anti-realist about the truthmakers. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Realism') | |
| A reaction: It is not quite clear how unreal truth makers could actually MAKE propositions true, rather than just being correlated with them. |
| 18932 | The facts about the existence of truthmakers can't have a further explanation [Cameron] |
| Full Idea: The orthodox truthmaker theorist thinks the facts concerning the existence of the truthmakers do not admit of further explanation. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 6) | |
| A reaction: It is fairly obvious, I suppose, that not every truth can have a truthmaker, just as the verification principle could not be verified, and you can't perceive your perception in order to check it. Could God withdraw the power of truthmaking? |
| 15394 | Truthmaker requires a commitment to tropes or states of affairs, for contingent truths [Cameron] |
| Full Idea: The most popular view is that an object is a truthmaker if the object couldn't exist and the truth be false. But contingent predications are also held to need truthmakers. Socrates is not necessarily snub-nosed, so a trope or state of affairs is needed. | |
| From: Ross P. Cameron (Intrinsic and Extrinsic Properties [2009], 'Truthmakers') | |
| A reaction: Cameron calls this 'some heavy ontological commitments'. If snub-nosedness is necessitated by the trope of 'being snub-nosed', what is the truthmaker for Socrates having that trope? |
| 18869 | Without truthmakers, negative truths must be ungrounded [Cameron] |
| Full Idea: If negative truths don't have truthmakers then make no mistake: they are ungrounded. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Max and Nec') | |
| A reaction: What would be the grounding for truths which expressed the necessary preconditions for all existence? Could 'nothing whatever exists' ever be a truth? |
| 18923 | The present property 'having been F' says nothing about a thing's intrinsic nature [Cameron] |
| Full Idea: The property 'being such as to have been a child' is suspicious because it points beyond its instances in the sense that a thing's presently having that property tells us nothing about the present intrinsic nature of the thing. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 2) | |
| A reaction: This is his objection to what he calls the 'Lucretian' strategy, which tries to make history into a property of present reality. That is implausible, I think, because there is no test for the property, apart from knowledge of the past. Reality is tensed? |
| 18926 | One temporal distibution property grounds our present and past truths [Cameron] |
| Full Idea: Temporal distributional properties are fundamental - it is exactly the same property that is grounding the truth about how the bearer now is that is grounding truths about how the bearer was. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 4) | |
| A reaction: Some kind of slight of hand is going on here, though he does a nice job of confronting all possible objections. This is the sort of metaphysics you come up with when you stake everything on the dubious notion of a 'property'. |
| 18929 | We don't want present truthmakers for the past, if they are about to cease to exist! [Cameron] |
| Full Idea: Whilst not logically inconsistent, it would be bad if it could now be true that ten years ago there was a sea battle, but that five years ago it wasn't true that five years before that there was a sea battle. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 4) | |
| A reaction: Nicely makes the point that you can't let the past rely on truthmakers in the present, if those truthmakers are about to go out of existence. So you need a sustained truthmaker, without giving up presentism. Enter 'temporally distributed properties'? |
| 18871 | I support the correspondence theory because I believe in truthmakers [Cameron] |
| Full Idea: I tend to think that the fundamental reason we can have the correspondence theory of truth is that truthmaker theory is correct. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Max and Nec') | |
| A reaction: [This responds to Fumerton 2006, who gives the opposite view] Cameron gives himself the classic problem of spelling out the correspondence relation (perhaps as 'congruence'). I like truthmaking, but I'm unsure about correspondence. |
| 18870 | Maybe truthmaking and correspondence stand together, and are interdefinable [Cameron] |
| Full Idea: One view says truthmaker theory stands or falls with the correspondence theory of truth, because the truthmaker for p is just the portion of reality that p corresponds to: truthmaker and correspondence can be conversely defined. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Max and Nec') | |
| A reaction: The normal view, which I prefer, is that correspondence is a particular theory of truthmaking, invoking a precise 'correspondence' relation. Hence abolishing correspondence would not abolish truthmaking, if you had a rival account. |
| 15102 | S4 says there must be some necessary truths (the actual ones, of which there is at least one) [Cameron] |
| Full Idea: S4 says there must be some necessary truths, because the actual necessary truths must be necessary. (It says if there are some actual necessary truths then that is so - but the S4 axiom is an actual necessary truth, if true). | |
| From: Ross P. Cameron (On the Source of Necessity [2010], 2) |
| 18194 | 'Forcing' can produce new models of ZFC from old models [Maddy] |
| Full Idea: Cohen's method of 'forcing' produces a new model of ZFC from an old model by appending a carefully chosen 'generic' set. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.4) |
| 18195 | A Large Cardinal Axiom would assert ever-increasing stages in the hierarchy [Maddy] |
| Full Idea: A possible axiom is the Large Cardinal Axiom, which asserts that there are more and more stages in the cumulative hierarchy. Infinity can be seen as the first of these stages, and Replacement pushes further in this direction. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.5) |
| 13011 | New axioms are being sought, to determine the size of the continuum [Maddy] |
| Full Idea: In current set theory, the search is on for new axioms to determine the size of the continuum. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §0) | |
| A reaction: This sounds the wrong way round. Presumably we seek axioms that fix everything else about set theory, and then check to see what continuum results. Otherwise we could just pick our continuum, by picking our axioms. |
| 13013 | The Axiom of Extensionality seems to be analytic [Maddy] |
| Full Idea: Most writers agree that if any sense can be made of the distinction between analytic and synthetic, then the Axiom of Extensionality should be counted as analytic. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.1) | |
| A reaction: [Boolos is the source of the idea] In other words Extensionality is not worth discussing, because it simply tells you what the world 'set' means, and there is no room for discussion about that. The set/class called 'humans' varies in size. |
| 13014 | Extensional sets are clearer, simpler, unique and expressive [Maddy] |
| Full Idea: The extensional view of sets is preferable because it is simpler, clearer, and more convenient, because it individuates uniquely, and because it can simulate intensional notions when the need arises. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.1) | |
| A reaction: [She cites Fraenkel, Bar-Hillet and Levy for this] The difficulty seems to be whether the extensional notion captures our ordinary intuitive notion of what constitutes a group of things, since that needs flexible size and some sort of unity. |
| 13021 | The Axiom of Infinity states Cantor's breakthrough that launched modern mathematics [Maddy] |
| Full Idea: The Axiom of Infinity is a simple statement of Cantor's great breakthrough. His bold hypothesis that a collection of elements that had lurked in the background of mathematics could be infinite launched modern mathematics. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.5) | |
| A reaction: It also embodies one of those many points where mathematics seems to depart from common sense - but then most subjects depart from common sense when they get more sophisticated. Look what happened to art. |
| 13022 | Infinite sets are essential for giving an account of the real numbers [Maddy] |
| Full Idea: If one is interested in analysis then infinite sets are indispensable since even the notion of a real number cannot be developed by means of finite sets alone. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.5) | |
| A reaction: [Maddy is citing Fraenkel, Bar-Hillel and Levy] So Cantor's great breakthrough (Idea 13021) actually follows from the earlier acceptance of the real numbers, so that's where the departure from common sense started. |
| 18191 | Axiom of Infinity: completed infinite collections can be treated mathematically [Maddy] |
| Full Idea: The axiom of infinity: that there are infinite sets is to claim that completed infinite collections can be treated mathematically. In its standard contemporary form, the axioms assert the existence of the set of all finite ordinals. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.3) |
| 13023 | The Power Set Axiom is needed for, and supported by, accounts of the continuum [Maddy] |
| Full Idea: The Power Set Axiom is indispensable for a set-theoretic account of the continuum, ...and in so far as those attempts are successful, then the power-set principle gains some confirmatory support. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.6) | |
| A reaction: The continuum is, of course, notoriously problematic. Have we created an extra problem in our attempts at solving the first one? |
| 18193 | The Axiom of Foundation says every set exists at a level in the set hierarchy [Maddy] |
| Full Idea: In the presence of other axioms, the Axiom of Foundation is equivalent to the claim that every set is a member of some Vα. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.3) |
| 13024 | Efforts to prove the Axiom of Choice have failed [Maddy] |
| Full Idea: Jordain made consistent and ill-starred efforts to prove the Axiom of Choice. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.7) | |
| A reaction: This would appear to be the fate of most axioms. You would presumably have to use a different system from the one you are engaged with to achieve your proof. |
| 13025 | Modern views say the Choice set exists, even if it can't be constructed [Maddy] |
| Full Idea: Resistance to the Axiom of Choice centred on opposition between existence and construction. Modern set theory thrives on a realistic approach which says the choice set exists, regardless of whether it can be defined, constructed, or given by a rule. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.7) | |
| A reaction: This seems to be a key case for the ontology that lies at the heart of theory. Choice seems to be an invaluable tool for proofs, so it won't go away, so admit it to the ontology. Hm. So the tools of thought have existence? |
| 13026 | A large array of theorems depend on the Axiom of Choice [Maddy] |
| Full Idea: Many theorems depend on the Axiom of Choice, including that a countable union of sets is countable, and results in analysis, topology, abstract algebra and mathematical logic. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.7) | |
| A reaction: The modern attitude seems to be to admit anything if it leads to interesting results. It makes you wonder about the modern approach of using mathematics and logic as the cutting edges of ontological thinking. |
| 17610 | The Axiom of Choice paradoxically allows decomposing a sphere into two identical spheres [Maddy] |
| Full Idea: One feature of the Axiom of Choice that troubled many mathematicians was the so-called Banach-Tarski paradox: using the Axiom, a sphere can be decomposed into finitely many parts and those parts reassembled into two spheres the same size as the original. | |
| From: Penelope Maddy (Defending the Axioms [2011], 1.3) | |
| A reaction: (The key is that the parts are non-measurable). To an outsider it is puzzling that the Axiom has been universally accepted, even though it produces such a result. Someone can explain that, I'm sure. |
| 18169 | Axiom of Reducibility: propositional functions are extensionally predicative [Maddy] |
| Full Idea: The Axiom of Reducibility states that every propositional function is extensionally equivalent to some predicative proposition function. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.1) |
| 13019 | The Iterative Conception says everything appears at a stage, derived from the preceding appearances [Maddy] |
| Full Idea: The Iterative Conception (Zermelo 1930) says everything appears at some stage. Given two objects a and b, let A and B be the stages at which they first appear. Suppose B is after A. Then the pair set of a and b appears at the immediate stage after B. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.3) | |
| A reaction: Presumably this all happens in 'logical time' (a nice phrase I have just invented!). I suppose we might say that the existence of the paired set is 'forced' by the preceding sets. No transcendental inferences in this story? |
| 13018 | Limitation of Size is a vague intuition that over-large sets may generate paradoxes [Maddy] |
| Full Idea: The 'limitation of size' is a vague intuition, based on the idea that being too large may generate the paradoxes. | |
| From: Penelope Maddy (Believing the Axioms I [1988], §1.3) | |
| A reaction: This is an intriguing idea to be found right at the centre of what is supposed to be an incredibly rigorous system. |
| 17824 | The master science is physical objects divided into sets [Maddy] |
| Full Idea: The master science can be thought of as the theory of sets with the entire range of physical objects as ur-elements. | |
| From: Penelope Maddy (Sets and Numbers [1981], II) | |
| A reaction: This sounds like Quine's view, since we have to add sets to our naturalistic ontology of objects. It seems to involve unrestricted mereology to create normal objects. |
| 8755 | Maddy replaces pure sets with just objects and perceived sets of objects [Maddy, by Shapiro] |
| Full Idea: Maddy dispenses with pure sets, by sketching a strong set theory in which everything is either a physical object or a set of sets of ...physical objects. Eventually a physiological story of perception will extend to sets of physical objects. | |
| From: report of Penelope Maddy (Realism in Mathematics [1990]) by Stewart Shapiro - Thinking About Mathematics 8.3 | |
| A reaction: This doesn't seem to find many supporters, but if we accept the perception of resemblances as innate (as in Hume and Quine), it is isn't adding much to see that we intrinsically see things in groups. |
| 10594 | Henkin semantics is more plausible for plural logic than for second-order logic [Maddy] |
| Full Idea: Henkin-style semantics seem to me more plausible for plural logic than for second-order logic. | |
| From: Penelope Maddy (Second Philosophy [2007], III.8 n1) | |
| A reaction: Henkin-style semantics are presented by Shapiro as the standard semantics for second-order logic. |
| 17620 | Critics of if-thenism say that not all starting points, even consistent ones, are worth studying [Maddy] |
| Full Idea: If-thenism denies that mathematics is in the business of discovering truths about abstracta. ...[their opponents] obviously don't regard any starting point, even a consistent one, as equally worthy of investigation. | |
| From: Penelope Maddy (Defending the Axioms [2011], 3.3) | |
| A reaction: I have some sympathy with if-thenism, in that you can obviously study the implications of any 'if' you like, but deep down I agree with the critics. |
| 18168 | 'Propositional functions' are propositions with a variable as subject or predicate [Maddy] |
| Full Idea: A 'propositional function' is generated when one of the terms of the proposition is replaced by a variable, as in 'x is wise' or 'Socrates'. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.1) | |
| A reaction: This implies that you can only have a propositional function if it is derived from a complete proposition. Note that the variable can be in either subject or in predicate position. It extends Frege's account of a concept as 'x is F'. |
| 17605 | Hilbert's geometry and Dedekind's real numbers were role models for axiomatization [Maddy] |
| Full Idea: At the end of the nineteenth century there was a renewed emphasis on rigor, the central tool of which was axiomatization, along the lines of Hilbert's axioms for geometry and Dedekind's axioms for real numbers. | |
| From: Penelope Maddy (Defending the Axioms [2011], 1.3) |
| 17625 | If two mathematical themes coincide, that suggest a single deep truth [Maddy] |
| Full Idea: The fact that two apparently fruitful mathematical themes turn out to coincide makes it all the more likely that they're tracking a genuine strain of mathematical depth. | |
| From: Penelope Maddy (Defending the Axioms [2011], 5.3ii) |
| 18190 | Completed infinities resulted from giving foundations to calculus [Maddy] |
| Full Idea: The line of development that finally led to a coherent foundation for the calculus also led to the explicit introduction of completed infinities: each real number is identified with an infinite collection of rationals. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.3) | |
| A reaction: Effectively, completed infinities just are the real numbers. |
| 18171 | Cantor and Dedekind brought completed infinities into mathematics [Maddy] |
| Full Idea: Both Cantor's real number (Cauchy sequences of rationals) and Dedekind's cuts involved regarding infinite items (sequences or sets) as completed and subject to further manipulation, bringing the completed infinite into mathematics unambiguously. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.1 n39) | |
| A reaction: So it is the arrival of the real numbers which is the culprit for lumbering us with weird completed infinites, which can then be the subject of addition, multiplication and exponentiation. Maybe this was a silly mistake? |
| 17615 | Every infinite set of reals is either countable or of the same size as the full set of reals [Maddy] |
| Full Idea: One form of the Continuum Hypothesis is the claim that every infinite set of reals is either countable or of the same size as the full set of reals. | |
| From: Penelope Maddy (Defending the Axioms [2011], 2.4 n40) |
| 18172 | Infinity has degrees, and large cardinals are the heart of set theory [Maddy] |
| Full Idea: The stunning discovery that infinity comes in different degrees led to the theory of infinite cardinal numbers, the heart of contemporary set theory. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.1) | |
| A reaction: It occurs to me that these huge cardinals only exist in set theory. If you took away that prop, they would vanish in a puff. |
| 18175 | For any cardinal there is always a larger one (so there is no set of all sets) [Maddy] |
| Full Idea: By the mid 1890s Cantor was aware that there could be no set of all sets, as its cardinal number would have to be the largest cardinal number, while his own theorem shows that for any cardinal there is a larger. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.1) | |
| A reaction: There is always a larger cardinal because of the power set axiom. Some people regard that with suspicion. |
| 18196 | An 'inaccessible' cardinal cannot be reached by union sets or power sets [Maddy] |
| Full Idea: An 'inaccessible' cardinal is one that cannot be reached by taking unions of small collections of smaller sets or by taking power sets. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.5) | |
| A reaction: They were introduced by Hausdorff in 1908. |
| 18187 | Theorems about limits could only be proved once the real numbers were understood [Maddy] |
| Full Idea: Even the fundamental theorems about limits could not [at first] be proved because the reals themselves were not well understood. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.2) | |
| A reaction: This refers to the period of about 1850 (Weierstrass) to 1880 (Dedekind and Cantor). |
| 18182 | The extension of concepts is not important to me [Maddy] |
| Full Idea: I attach no decisive importance even to bringing in the extension of the concepts at all. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], §107) | |
| A reaction: He almost seems to equate the concept with its extension, but that seems to raise all sorts of questions, about indeterminate and fluctuating extensions. |
| 18177 | In the ZFC hierarchy it is impossible to form Frege's set of all three-element sets [Maddy] |
| Full Idea: In the ZFC cumulative hierarchy, Frege's candidates for numbers do not exist. For example, new three-element sets are formed at every stage, so there is no stage at which the set of all three-element sets could he formed. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.2) | |
| A reaction: Ah. This is a very important fact indeed if you are trying to understand contemporary discussions in philosophy of mathematics. |
| 18164 | Frege solves the Caesar problem by explicitly defining each number [Maddy] |
| Full Idea: To solve the Julius Caesar problem, Frege requires explicit definitions of the numbers, and he proposes his well-known solution: the number of Fs = the extension of the concept 'equinumerous with F' (based on one-one correspondence). | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.1) | |
| A reaction: Why do there have to be Fs before there can be the corresponding number? If there were no F for 523, would that mean that '523' didn't exist (even if 522 and 524 did exist)? |
| 17825 | Set theory (unlike the Peano postulates) can explain why multiplication is commutative [Maddy] |
| Full Idea: If you wonder why multiplication is commutative, you could prove it from the Peano postulates, but the proof offers little towards an answer. In set theory Cartesian products match 1-1, and n.m dots when turned on its side has m.n dots, which explains it. | |
| From: Penelope Maddy (Sets and Numbers [1981], II) | |
| A reaction: 'Turning on its side' sounds more fundamental than formal set theory. I'm a fan of explanation as taking you to the heart of the problem. I suspect the world, rather than set theory, explains the commutativity. |
| 17826 | Standardly, numbers are said to be sets, which is neat ontology and epistemology [Maddy] |
| Full Idea: The standard account of the relationship between numbers and sets is that numbers simply are certain sets. This has the advantage of ontological economy, and allows numbers to be brought within the epistemology of sets. | |
| From: Penelope Maddy (Sets and Numbers [1981], III) | |
| A reaction: Maddy votes for numbers being properties of sets, rather than the sets themselves. See Yourgrau's critique. |
| 17828 | Numbers are properties of sets, just as lengths are properties of physical objects [Maddy] |
| Full Idea: I propose that ...numbers are properties of sets, analogous, for example, to lengths, which are properties of physical objects. | |
| From: Penelope Maddy (Sets and Numbers [1981], III) | |
| A reaction: Are lengths properties of physical objects? A hole in the ground can have a length. A gap can have a length. Pure space seems to contain lengths. A set seems much more abstract than its members. |
| 10718 | A natural number is a property of sets [Maddy, by Oliver] |
| Full Idea: Maddy takes a natural number to be a certain property of sui generis sets, the property of having a certain number of members. | |
| From: report of Penelope Maddy (Realism in Mathematics [1990], 3 §2) by Alex Oliver - The Metaphysics of Properties | |
| A reaction: [I believe Maddy has shifted since then] Presumably this will make room for zero and infinities as natural numbers. Personally I want my natural numbers to count things. |
| 18184 | Making set theory foundational to mathematics leads to very fruitful axioms [Maddy] |
| Full Idea: The set theory axioms developed in producing foundations for mathematics also have strong consequences for existing fields, and produce a theory that is immensely fruitful in its own right. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.2) | |
| A reaction: [compressed] Second of Maddy's three benefits of set theory. This benefit is more questionable than the first, because the axioms may be invented because of their nice fruit, instead of their accurate account of foundations. |
| 18185 | Unified set theory gives a final court of appeal for mathematics [Maddy] |
| Full Idea: The single unified area of set theory provides a court of final appeal for questions of mathematical existence and proof. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.2) | |
| A reaction: Maddy's third benefit of set theory. 'Existence' means being modellable in sets, and 'proof' means being derivable from the axioms. The slightly ad hoc character of the axioms makes this a weaker defence. |
| 18183 | Set theory brings mathematics into one arena, where interrelations become clearer [Maddy] |
| Full Idea: Set theoretic foundations bring all mathematical objects and structures into one arena, allowing relations and interactions between them to be clearly displayed and investigated. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.2) | |
| A reaction: The first of three benefits of set theory which Maddy lists. The advantages of the one arena seem to be indisputable. |
| 18186 | Identifying geometric points with real numbers revealed the power of set theory [Maddy] |
| Full Idea: The identification of geometric points with real numbers was among the first and most dramatic examples of the power of set theoretic foundations. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.2) | |
| A reaction: Hence the clear definition of the reals by Dedekind and Cantor was the real trigger for launching set theory. |
| 18188 | The line of rationals has gaps, but set theory provided an ordered continuum [Maddy] |
| Full Idea: The structure of a geometric line by rational points left gaps, which were inconsistent with a continuous line. Set theory provided an ordering that contained no gaps. These reals are constructed from rationals, which come from integers and naturals. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.2) | |
| A reaction: This completes the reduction of geometry to arithmetic and algebra, which was launch 250 years earlier by Descartes. |
| 17618 | Set-theory tracks the contours of mathematical depth and fruitfulness [Maddy] |
| Full Idea: Our set-theoretic methods track the underlying contours of mathematical depth. ...What sets are, most fundamentally, is markers for these contours ...they are maximally effective trackers of certain trains of mathematical fruitfulness. | |
| From: Penelope Maddy (Defending the Axioms [2011], 3.4) | |
| A reaction: This seems to make it more like a map of mathematics than the actual essence of mathematics. |
| 18163 | Mathematics rests on the logic of proofs, and on the set theoretic axioms [Maddy] |
| Full Idea: Our much loved mathematical knowledge rests on two supports: inexorable deductive logic (the stuff of proof), and the set theoretic axioms. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I Intro) |
| 17830 | Number theory doesn't 'reduce' to set theory, because sets have number properties [Maddy] |
| Full Idea: I am not suggesting a reduction of number theory to set theory ...There are only sets with number properties; number theory is part of the theory of finite sets. | |
| From: Penelope Maddy (Sets and Numbers [1981], V) |
| 17827 | Sets exist where their elements are, but numbers are more like universals [Maddy] |
| Full Idea: A set of things is located where the aggregate of those things is located, ...but a number is simultaneously located at many different places (10 in my hand, and a baseball team) ...so numbers seem more like universals than particulars. | |
| From: Penelope Maddy (Sets and Numbers [1981], III) | |
| A reaction: My gut feeling is that Maddy's master idea (of naturalising sets by building them from ur-elements of natural objects) won't work. Sets can work fine in total abstraction from nature. |
| 17823 | If mathematical objects exist, how can we know them, and which objects are they? [Maddy] |
| Full Idea: The popular challenges to platonism in philosophy of mathematics are epistemological (how are we able to interact with these objects in appropriate ways) and ontological (if numbers are sets, which sets are they). | |
| From: Penelope Maddy (Sets and Numbers [1981], I) | |
| A reaction: These objections refer to Benacerraf's two famous papers - 1965 for the ontology, and 1973 for the epistemology. Though he relied too much on causal accounts of knowledge in 1973, I'm with him all the way. |
| 8756 | Intuition doesn't support much mathematics, and we should question its reliability [Maddy, by Shapiro] |
| Full Idea: Maddy says that intuition alone does not support very much mathematics; more importantly, a naturalist cannot accept intuition at face value, but must ask why we are justified in relying on intuition. | |
| From: report of Penelope Maddy (Realism in Mathematics [1990]) by Stewart Shapiro - Thinking About Mathematics 8.3 | |
| A reaction: It depends what you mean by 'intuition', but I identify with her second objection, that every faculty must ultimately be subject to criticism, which seems to point to a fairly rationalist view of things. |
| 17733 | We know mind-independent mathematical truths through sets, which rest on experience [Maddy, by Jenkins] |
| Full Idea: Maddy proposes that we can know (some) mind-independent mathematical truths through knowing about sets, and that we can obtain knowledge of sets through experience. | |
| From: report of Penelope Maddy (Realism in Mathematics [1990]) by Carrie Jenkins - Grounding Concepts 6.5 | |
| A reaction: Maddy has since backed off from this, and now tries to merely defend 'objectivity' about sets (2011:114). My amateurish view is that she is overrating the importance of sets, which merely model mathematics. Look at category theory. |
| 18204 | Scientists posit as few entities as possible, but set theorist posit as many as possible [Maddy] |
| Full Idea: Crudely, the scientist posits only those entities without which she cannot account for observations, while the set theorist posits as many entities as she can, short of inconsistency. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], II.5) |
| 18207 | Maybe applications of continuum mathematics are all idealisations [Maddy] |
| Full Idea: It could turn out that all applications of continuum mathematics in natural sciences are actually instances of idealisation. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], II.6) |
| 17614 | The connection of arithmetic to perception has been idealised away in modern infinitary mathematics [Maddy] |
| Full Idea: Ordinary perceptual cognition is most likely involved in our grasp of elementary arithmetic, but ...this connection to the physical world has long since been idealized away in the infinitary structures of contemporary pure mathematics. | |
| From: Penelope Maddy (Defending the Axioms [2011], 2.3) | |
| A reaction: Despite this, Maddy's quest is for a 'naturalistic' account of mathematics. She ends up defending 'objectivity' (and invoking Tyler Burge), rather than even modest realism. You can't 'idealise away' the counting of objects. I blame Cantor. |
| 17829 | Number words are unusual as adjectives; we don't say 'is five', and numbers always come first [Maddy] |
| Full Idea: Number words are not like normal adjectives. For example, number words don't occur in 'is (are)...' contexts except artificially, and they must appear before all other adjectives, and so on. | |
| From: Penelope Maddy (Sets and Numbers [1981], IV) | |
| A reaction: [She is citing Benacerraf's arguments] |
| 18167 | We can get arithmetic directly from HP; Law V was used to get HP from the definition of number [Maddy] |
| Full Idea: Recent commentators have noted that Frege's versions of the basic propositions of arithmetic can be derived from Hume's Principle alone, that the fatal Law V is only needed to derive Hume's Principle itself from the definition of number. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], I.1) | |
| A reaction: Crispin Wright is the famous exponent of this modern view. Apparently Charles Parsons (1965) first floated the idea. |
| 18875 | Realism says a discourse is true or false, and some of it is true [Cameron] |
| Full Idea: Realism about a discourse is 1) to think that the sentences are, when construed literally, literally true or false, and 2) to think that some of the sentences of the discourse are non-vacuously true. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Realism') | |
| A reaction: [Cameron adds 'non-vacuously' to an idea of Sayre-McCord 199 p.5] This is realism based on what is 'true', without specifying 'commitments', so I like it. Cameron says it makes mathematical postulationists into realists. He likes 'mind-independent'. |
| 18878 | Realism says truths rest on mind-independent reality; truthmaking theories are about which features [Cameron] |
| Full Idea: All that is necessary for realism, I claim, is that truth is grounded in mind-independent features of fundamental reality. Truthmaker theory comes into play because it is a theory about what those features are (…so it isn't a commitment to realism). | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Realism') | |
| A reaction: [He cites Michael Devitt for this approach] What is the word 'fundamental' doing here? Because the mind-dependent parts of reality are considered non-fundamental? The no-true-Scotsman-hates-whisky move? His truthmaking is committed to 'things'. |
| 18881 | For realists it is analytic that truths are grounded in the world [Cameron] |
| Full Idea: The analytic commitment of realism is that truths are grounded in the world. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Grounding') | |
| A reaction: Certain fifth-level truths might be a long way from the actual world, and deeply interfused with human concepts and theories. Negative truths must be fitted into this picture. |
| 18205 | The theoretical indispensability of atoms did not at first convince scientists that they were real [Maddy] |
| Full Idea: The case of atoms makes it clear that the indispensable appearance of an entity in our best scientific theory is not generally enough to convince scientists that it is real. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], II.6) | |
| A reaction: She refers to the period between Dalton and Einstein, when theories were full of atoms, but there was strong reluctance to actually say that they existed, until the direct evidence was incontrovertable. Nice point. |
| 18924 | Being polka-dotted is a 'spatial distribution' property [Cameron] |
| Full Idea: Spatial distribution properties say how things are across a region of space, such as being polka-dotted. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 3) | |
| A reaction: I think the routine fallacy of inferring properties from predicates is buried here. We truthfully describe it as 'polka-dotted', but that doesn't mean we must reify polka-dottedness, and see it as a feature of the world. What is a 'jumbled' space? |
| 15401 | Essentialists say intrinsic properties arise from what the thing is, irrespective of surroundings [Cameron] |
| Full Idea: The essentialist approach would be to say that an intrinsic property is one such that it is no part of what it is to instantiate that property that the bearer stands in some relation to its surroundings. | |
| From: Ross P. Cameron (Intrinsic and Extrinsic Properties [2009], 'Analysis') | |
| A reaction: This is offered as an alternative to the David Lewis account in terms of duplicates across possible worlds. You will have gathered by now, if you have spent days poring over my stuff, that I favour the essentialist approach. |
| 15393 | An object's intrinsic properties are had in virtue of how it is, independently [Cameron] |
| Full Idea: Intrinsic properties are those that an object has solely in virtue of how it is, independently of its surroundings. | |
| From: Ross P. Cameron (Intrinsic and Extrinsic Properties [2009], 'Intro') | |
| A reaction: Better not mention quantum mechanics and fields if you want to talk of objects being independent of their surroundings. Am I 'independent' of gravity, or is gravity 'independent' of me? |
| 15396 | Most criteria for identity over time seem to leave two later objects identical to the earlier one [Cameron] |
| Full Idea: Criteria for identity across times have proven hard to give. Whatever criteria we lay down, it seems that there are possible situations in which two later objects bear the relevant relation to one earlier object, though only one of them can be identical. | |
| From: Ross P. Cameron (Intrinsic and Extrinsic Properties [2009], 'Personal') | |
| A reaction: We only have to think of twins, amoebae that fission, and the Ship of Theseus. We seem to end up inventing a dubious criterion in order to break the tie. |
| 18930 | Change is instantiation of a non-uniform distributional property, like 'being red-then-orange' [Cameron] |
| Full Idea: What change is on the account being offered is to instantiate a non-uniform distributional property. Being red at one time and orange at a later time is to be analysed as instantiating the distributional property 'being red-then-orange'. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 4) | |
| A reaction: One of those moments when you begin to doubt whether 'being analysed' successfully actually adds much to our wisdom. His property sounds suspiciously 'gruesome' - i.e. subject to the vagaries of how we chose to describe the thing. |
| 15103 | Blackburn fails to show that the necessary cannot be grounded in the contingent [Cameron] |
| Full Idea: I conclude that Blackburn has not shown that any grounding of the necessary in the contingent (the Contingency Horn of his dilemma) is doomed to failure. | |
| From: Ross P. Cameron (On the Source of Necessity [2010], 2) | |
| A reaction: [You must read the article for details of Cameron's argument!] He goes on to also reject the Necessity Horn (that there is a regress if necessities must rely on necessities). |
| 18872 | We should reject distinct but indiscernible worlds [Cameron] |
| Full Idea: I think we should reject distinct but indiscernible worlds. | |
| From: Ross P. Cameron (Truthmakers, Realism and Ontology [2008], 'Max and Nec') | |
| A reaction: An interesting passing remark. Presumably there would be unknowable truths about such worlds, which wouldn't bother a full-blooded realist. Indiscernible to whom? Me? Humanity? A divine mind? |
| 18206 | Science idealises the earth's surface, the oceans, continuities, and liquids [Maddy] |
| Full Idea: In science we treat the earth's surface as flat, we assume the ocean to be infinitely deep, we use continuous functions for what we know to be quantised, and we take liquids to be continuous despite atomic theory. | |
| From: Penelope Maddy (Naturalism in Mathematics [1997], II.6) | |
| A reaction: If fussy people like scientists do this all the time, how much more so must the confused multitude be doing the same thing all day? |
| 15104 | The 'moving spotlight' theory makes one time privileged, while all times are on a par ontologically [Cameron] |
| Full Idea: What seems so wrong about the 'moving spotlight' theory is that here one time is privileged, but all the times are on a par ontologically. | |
| From: Ross P. Cameron (On the Source of Necessity [2010], 4) | |
| A reaction: The whole thing is baffling, but this looks like a good point. All our intuitions make presentism (there's only the present) look like a better theory than the moving spotlight (that the present is just 'special'). |
| 18927 | Surely if things extend over time, then time itself must be extended? [Cameron] |
| Full Idea: If there are temporally extended entities - and there are - then there must be extended regions of time for those entities to extend in. Hence presentism is false. | |
| From: Ross P. Cameron (Truthmaking for Presentists [2011], 4) | |
| A reaction: [Cameron is playing devil's advocate] Something has to be weird here, and I take it to be the fact that the past no longer exists, and yet it is fixed and supports truths. Get over it. My childhood has gone. Totally. Irrevocably. |
| 1513 | The Egyptians were the first to say the soul is immortal and reincarnated [Herodotus] |
| Full Idea: The Egyptians were the first to claim that the soul of a human being is immortal, and that each time the body dies the soul enters another creature just as it is being born. | |
| From: Herodotus (The Histories [c.435 BCE], 2.123.2) |