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All the ideas for 'Thinking About Mathematics', 'Possibility' and 'fragments/reports'

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62 ideas

1. Philosophy / F. Analytic Philosophy / 4. Conceptual Analysis
If an analysis shows the features of a concept, it doesn't seem to 'reduce' the concept [Jubien]
     Full Idea: An analysis of a concept tells us what the concept is by telling us what its constituents are and how they are combined. ..The features of the concept are present in the analysis, making it surprising the 'reductive' analyses are sought.
     From: Michael Jubien (Possibility [2009], 4.5)
     A reaction: He says that there are nevertheless reductive analyses, such as David Lewis's analysis of modality. We must disentangle conceptual analysis from causal analysis (e.g. in his example of the physicalist reduction of mind).
5. Theory of Logic / A. Overview of Logic / 3. Value of Logic
It is a mistake to think that the logic developed for mathematics can clarify language and philosophy [Jubien]
     Full Idea: It has often been uncritically assumed that logic that was initially a tool for clarifying mathematics could be seamlessly and uniformly applied in the effort to clarify ordinary language and philosophy, but this has been a real mistake.
     From: Michael Jubien (Possibility [2009], Intro)
     A reaction: I'm not saying he's right (since you need stupendous expertise to make that call) but my intuitions are that he has a good point, and he is at least addressing a crucial question which most analytical philosophers avert their eyes from.
5. Theory of Logic / D. Assumptions for Logic / 2. Excluded Middle
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.
5. Theory of Logic / F. Referring in Logic / 1. Naming / a. Names
We only grasp a name if we know whether to apply it when the bearer changes [Jubien]
     Full Idea: We cannot be said to have a full grasp of a name unless we have a definite disposition to apply it or to withhold it under whatever conceivable changes the bearer of the name might come to undergo.
     From: Michael Jubien (Possibility [2009], 5.3)
     A reaction: This is right, and an excellent counterproposal to the logicians' notion that names have to rigidly designate. As a bare minimum, you are not supposed to deny the identity of your parents because they have grown a bit older, or a damaged painting.
The baptiser picks the bearer of a name, but social use decides the category [Jubien]
     Full Idea: The person who introduces a proper name gets to pick its bearer, but its category - and consequently the meaning of the name - is determined by social use.
     From: Michael Jubien (Possibility [2009], 7)
     A reaction: New 'division of labour'. The idea that a name has some sort of meaning seems right and important. If babies were switched after baptism, social use might fix the name to the new baby. The namer could stipulate the category at the baptism. Too neat.
5. Theory of Logic / F. Referring in Logic / 1. Naming / c. Names as referential
Examples show that ordinary proper names are not rigid designators [Jubien]
     Full Idea: There are plenty of examples to show that ordinary proper names simply are not rigid designators.
     From: Michael Jubien (Possibility [2009], 5.1)
     A reaction: His examples are the planet Venus and the dust of which it is formed, and a statue made of clay. In other words, for some objects, perhaps under certain descriptions (e.g. functional ones), the baptised matter can change. Rigidity is an extra topping.
5. Theory of Logic / F. Referring in Logic / 2. Descriptions / b. Definite descriptions
We could make a contingent description into a rigid and necessary one by adding 'actual' to it [Jubien]
     Full Idea: 'The winner of the Derby' satisfies some horse, but only accidentally. But we could 'rigidify' the description by inserting 'actual' into it, giving 'the actual winner of the Derby'. Winning is a contingent property, but actually winning is necessary.
     From: Michael Jubien (Possibility [2009], 5.1)
     A reaction: I like this unusual proposal because instead of switching into formal logic in order to capture the ideas we are after, he is drawing on the resources of ordinary language, offering philosophers a way of speaking plain English more precisely.
5. Theory of Logic / G. Quantification / 3. Objectual Quantification
Philosophers reduce complex English kind-quantifiers to the simplistic first-order quantifier [Jubien]
     Full Idea: There is a readiness of philosophers to 'translate' English, with its seeming multitude of kind-driven quantifiers, into first-order logic, with its single wide-open quantifier.
     From: Michael Jubien (Possibility [2009], 4.1)
     A reaction: As in example he says that reference to a statue involves a 'statue-quantifier'. Thus we say things about the statue that we would not say about the clay, which would involve a 'clay-quantifier'.
6. Mathematics / A. Nature of Mathematics / 2. Geometry
No perceptible object is truly straight or curved [Protagoras]
     Full Idea: No perceptible object is geometrically straight or curved; after all, a circle does not touch a ruler at a point, as Protagoras used to say, in arguing against the geometers.
     From: Protagoras (fragments/reports [c.441 BCE], B07), quoted by Aristotle - Metaphysics 998a1
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / b. Types of number
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.
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / h. Reals from Cauchy
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.
6. Mathematics / B. Foundations for Mathematics / 1. Foundations for Mathematics
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.
6. Mathematics / B. Foundations for Mathematics / 5. Definitions of Number / f. Zermelo numbers
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.
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / a. Structuralism
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.
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.
6. Mathematics / C. Sources of Mathematics / 6. Logicism / d. Logicism critique
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.
6. Mathematics / C. Sources of Mathematics / 7. Formalism
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.
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.
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.
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / b. Intuitionism
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.
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / c. Conceptualism
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.
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / d. Predicativism
'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.
7. Existence / A. Nature of Existence / 3. Being / g. Particular being
To exist necessarily is to have an essence whose own essence must be instantiated [Jubien]
     Full Idea: For a thing to exist necessarily is for it to have an entity-essence whose own entity-essence entails being instantiated.
     From: Michael Jubien (Possibility [2009], 6.4)
     A reaction: This is the culmination of a lengthy discussion, and is not immediately persuasive. For Jubien the analysis rests on a platonist view of properties, which doesn't help.
7. Existence / C. Structure of Existence / 8. Stuff / a. Pure stuff
If objects are just conventional, there is no ontological distinction between stuff and things [Jubien]
     Full Idea: Under the Quinean (conventional) view of objects, there is no ontological distinction between stuff and things.
     From: Michael Jubien (Possibility [2009], 1.5)
     A reaction: This is the bold nihilistic account of physical objects, which seems to push all of our ontology into language (English?). We could devise divisions into things that were just crazy, and likely to lead to the rapid extinction of creatures who did it.
7. Existence / E. Categories / 1. Categories
The category of Venus is not 'object', or even 'planet', but a particular class of good-sized object [Jubien]
     Full Idea: The category of Venus is not 'physical object' or 'mereological sum', but narrower. Surprisingly, it is not 'planet', since it might cease to be a planet and still merit the name 'Venus'. It is something like 'well-integrated, good-sized physical object'.
     From: Michael Jubien (Possibility [2009], 5.3)
     A reaction: Jubien is illustrating Idea 13402. This is a nice demonstration of how one might go about the task of constructing categories - by showing the modal profiles of things to which names have been assigned. Categories are file names.
9. Objects / A. Existence of Objects / 5. Individuation / a. Individuation
The idea that every entity must have identity conditions is an unfortunate misunderstanding [Jubien]
     Full Idea: The pervasiveness, throughout philosophy, of the assumption that entities of various kinds need identity conditions is one unfortunate aspect of Quine's important philosophical legacy.
     From: Michael Jubien (Possibility [2009], Intro)
     A reaction: Lowe seems to be an example of a philosopher who habitually demands individuation conditions for everything that is referred to. Presumably the alternative is to take lots of things as primitive, but this seems to be second best.
9. Objects / A. Existence of Objects / 5. Individuation / d. Individuation by haecceity
Any entity has the unique property of being that specific entity [Jubien]
     Full Idea: For any entity of any sort, abstract or concrete, I assume there is a property of being that specific entity. For want of a better term, I will call such properties entity-essences. They are 'singulary' - not instantiable by more than one thing at a time.
     From: Michael Jubien (Possibility [2009], 4.2)
     A reaction: Baffling. Why would someone who has mocked all sorts of bogus philosophical claims based on logic then go on to assert the existence of such weird things as these? I can't make sense of this property being added to a thing's other properties.
9. Objects / A. Existence of Objects / 5. Individuation / e. Individuation by kind
It is incoherent to think that a given entity depends on its kind for its existence [Jubien]
     Full Idea: It is simply far-fetched - even incoherent - to think that, given an entity, of whatever kind, its being a single entity somehow consists in its satisfying some condition involving the kind to which it belongs (or concepts related to that kind).
     From: Michael Jubien (Possibility [2009], 2.3)
     A reaction: Well said. I can't see how philosophers have allowed themselves to drift into such a daft view. Kinds blatantly depend on the individuals that constitute them, so how could the identity of the individuals depend on their kind?
9. Objects / A. Existence of Objects / 6. Nihilism about Objects
Objects need conventions for their matter, their temporal possibility, and their spatial possibility [Jubien]
     Full Idea: We need a first convention to determine what matter constitutes objects, then a second to determine whether there are different temporal possibilities for a given object, then a third for different spatial possibilities.
     From: Michael Jubien (Possibility [2009], 1.5)
     A reaction: This is building up a Quinean account of objects, as mere matter in regions of spacetime, which are then precisely determined by a set of social conventions.
Basically, the world doesn't have ready-made 'objects'; we carve objects any way we like [Jubien]
     Full Idea: There is a certain - very mild - sense in which I don't think the physical world comes with ready-made objects. I think instead that we (conventionally) carve it up into objects, and this can be done any way we like.
     From: Michael Jubien (Possibility [2009], 1.5)
     A reaction: I have no idea how one could begin to refute such a view. Obviously there are divisions (even if only of physical density) in the world, but nothing obliges us to make divisions at those points. We happily accept objects with gaps in them.
9. Objects / B. Unity of Objects / 3. Unity Problems / c. Statue and clay
If the statue is loved and the clay hated, that is about the object first qua statue, then qua clay [Jubien]
     Full Idea: If a sculptor says 'I love the statue but I really hate that piece of clay - it is way too hard to work with' ...the statement is partly is partly about that object qua statue and partly about that object qua piece of clay.
     From: Michael Jubien (Possibility [2009], 1.4)
     A reaction: His point is that identity is partly determined by the concept or category under which the thing falls. Plausible. Lots of identity muddles seem to come from our conceptual scheme not being quite up to the job when things change.
If one entity is an object, a statue, and some clay, these come apart in at least three ways [Jubien]
     Full Idea: A single entity is a physical object, a piece of clay and a statue. We seem to have that the object could be scattered, but not the other two; the object and the clay could be spherical, but not the statue; and only the object could have different matter.
     From: Michael Jubien (Possibility [2009], 5.2)
     A reaction: His proposal, roughly, is to reduce object-talk to property-talk, and then see the three views of this object as referring to different sets of properties, rather than to a single thing. Promising, except that he goes platonist about properties.
9. Objects / B. Unity of Objects / 3. Unity Problems / d. Coincident objects
The idea of coincident objects is a last resort, as it is opposed to commonsense naturalism [Jubien]
     Full Idea: I find it surprising that some philosophers accept 'coincident objects'. This notion clearly offends against commonsense 'naturalism' about the world, so it should be viewed as a last resort.
     From: Michael Jubien (Possibility [2009], 5.2 n9)
     A reaction: I'm not quite clear why he invokes 'naturalism', but I pass on his intuition because it seems right to me.
9. Objects / C. Structure of Objects / 8. Parts of Objects / a. Parts of objects
Parts seem to matter when it is just an object, but not matter when it is a kind of object [Jubien]
     Full Idea: When thought of just as an object, the parts of a thing seem definitive and their arrangement seems inconsequential. But when thought of as an object of a familiar kind it is reversed: the arrangement is important and the parts are inessential.
     From: Michael Jubien (Possibility [2009], 1.4)
     A reaction: This is analogous to the Ship of Theseus, where we say that the tour operator and the museum keeper give different accounts of whether it is the same ship. The 'kind' Jubien refers to is most likely to be a functional kind.
9. Objects / D. Essence of Objects / 7. Essence and Necessity / b. Essence not necessities
We should not regard essentialism as just nontrivial de re necessity [Jubien]
     Full Idea: I argue against the widely accepted characterization of the doctrine of 'essentialism' as the acceptance of nontrivial de re necessity
     From: Michael Jubien (Possibility [2009], Intro)
     A reaction: I agree entirely. The notion of an essence is powerful if clearly distinguished. The test is: can everything being said about essences be just as easily said by referring to necessities? If so, you are talking about the wrong thing.
9. Objects / E. Objects over Time / 9. Ship of Theseus
Thinking of them as 'ships' the repaired ship is the original, but as 'objects' the reassembly is the original [Jubien]
     Full Idea: Thinking about the original ship as a ship, we think we continue to have the 'same ship' as each part is replaced; ...but when we think of them as physical objects, we think the original ship and the outcome of the reassembly are one and the same.
     From: Michael Jubien (Possibility [2009], 1.4)
     A reaction: It seems to me that you cannot eliminate how we are thinking of the ship as influencing how we should read it. My suggestion is to think of Theseus himself valuing either the repaired or the reassembled version. That's bad for Jubien's account.
Rearranging the planks as a ship is confusing; we'd say it was the same 'object' with a different arrangement [Jubien]
     Full Idea: That the planks are rearranged as a ship elevates the sense of mystery, because arrangements matter for ships, but if they had been arranged differently we would have the same intuition - that it still counts as the same object.
     From: Michael Jubien (Possibility [2009], 1.4)
     A reaction: Implausible. Classic case: can I have my pen back? - smashes it to pieces and hands it over with 'there you are' - that's not my pen! - Jubien says it's the same object! - it isn't my pen, and it isn't the same object either! Where is Shelley's skylark?
9. Objects / F. Identity among Objects / 7. Indiscernible Objects
If two objects are indiscernible across spacetime, how could we decide whether or not they are the same? [Jubien]
     Full Idea: If a bit of matter has a qualitatively indistinguishable object located at a later time, with a path of spacetime connecting them, how could we determine they are identical? Neither identity nor diversity follows from qualitative indiscernibility.
     From: Michael Jubien (Possibility [2009], 1.3)
     A reaction: All these principles expounded by Leibniz were assumed to be timeless, but for identity over time the whole notion of things retaining identity despite changing has to be rethought. Essentialism to the rescue.
10. Modality / A. Necessity / 6. Logical Necessity
Entailment does not result from mutual necessity; mutual necessity ensures entailment [Jubien]
     Full Idea: Typically philosophers say that for P to entail Q is for the proposition that all P's are Q's to be necessary. I think this analysis is backwards, and that necessity rests on entailment, not vice versa.
     From: Michael Jubien (Possibility [2009], 4.4)
     A reaction: His example is that being a horse and being an animal are such that one entails the other. In other words, necessities arise out of property relations (which for Jubien are necessary because the properties are platonically timeless). Wrong.
10. Modality / C. Sources of Modality / 1. Sources of Necessity
Modality concerns relations among platonic properties [Jubien]
     Full Idea: I think modality has to do with relations involving the abstract part of the world, specifically with relations among (Platonic) properties.
     From: Michael Jubien (Possibility [2009], 3.2)
     A reaction: [Sider calls Jubien's the 'governance' view, since abstract relations govern the concrete] I take Jubien here (having done a beautiful demolition job on the possible worlds account of modality) to go spectacularly wrong. Modality starts in the concrete.
To analyse modality, we must give accounts of objects, properties and relations [Jubien]
     Full Idea: The ultimate analysis of possibility and necessity depends on two important ontological decisions: the choice of an analysis of the intuitive concept of a physical object, and the other is the positing of properties and relations.
     From: Michael Jubien (Possibility [2009], Intro)
     A reaction: In the same passage he adopts Quine's view of objects, leading to mereological essentialism, and a Platonic view of properties, based on Lewis's argument for taking some things at face value. One might start with processes and events instead.
10. Modality / E. Possible worlds / 1. Possible Worlds / e. Against possible worlds
The love of possible worlds is part of the dream that technical logic solves philosophical problems [Jubien]
     Full Idea: I believe the contemporary infatuation with possible worlds in philosophy stems in part from a tendency to think that technical logic offers silver-bullet solutions to philosophical problems.
     From: Michael Jubien (Possibility [2009], 3.2)
     A reaction: I would say that the main reason for the infatuation is just novelty. As a technical device it was only invented in the 1960s, so we are in a honeymoon period, as we would be with any new gadget. I can't imagine possible worlds figuring much in 100 years.
Possible worlds don't explain necessity, because they are a bunch of parallel contingencies [Jubien]
     Full Idea: The fundamental problem is that in world theory, what passes for necessity is in effect just a bunch of parallel 'contingencies'.
     From: Michael Jubien (Possibility [2009], 3.2)
     A reaction: Jubien's general complaint is that there is no connection between the possible worlds and the actual world, so they are irrelevant, but this is a nicely different point - that lots of contingent worlds can't add up to necessity. Nice.
11. Knowledge Aims / C. Knowing Reality / 2. Phenomenalism
Everything that exists consists in being perceived [Protagoras]
     Full Idea: Everything that exists consists in being perceived.
     From: Protagoras (fragments/reports [c.441 BCE]), quoted by Didymus the Blind - Commentary on the Psalms (frags)
     A reaction: A striking anticipation of Berkeley's "esse est percipi" (to be is to be perceived).
12. Knowledge Sources / C. Rationalism / 1. Rationalism
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.
13. Knowledge Criteria / D. Scepticism / 1. Scepticism
Protagoras was the first to claim that there are two contradictory arguments about everything [Protagoras, by Diog. Laertius]
     Full Idea: Protagoras was the first to claim that there are two contradictory arguments about everything.
     From: report of Protagoras (fragments/reports [c.441 BCE], A01) by Diogenes Laertius - Lives of Eminent Philosophers 09.51
13. Knowledge Criteria / E. Relativism / 1. Relativism
Man is the measure of all things - of things that are, and of things that are not [Protagoras]
     Full Idea: He began one of his books as follows: 'Man is the measure of all things - of the things that are, that they are, and of the things that are not, that they are not'.
     From: Protagoras (fragments/reports [c.441 BCE], B01), quoted by Diogenes Laertius - Lives of Eminent Philosophers 09.51
There is no more purely metaphysical doctrine than Protagorean relativism [Benardete,JA on Protagoras]
     Full Idea: No purer metaphysical doctrine can possibly be found than the Protagorean thesis that to be (anything at all) is to be relative ( to something or other).
     From: comment on Protagoras (fragments/reports [c.441 BCE]) by José A. Benardete - Metaphysics: the logical approach Ch.3
13. Knowledge Criteria / E. Relativism / 3. Subjectivism
You can only state the problem of the relative warmth of an object by agreeing on the underlying object [Benardete,JA on Protagoras]
     Full Idea: Only if the thing that is cold to me is precisely identical with the thing that is not cold to you can Protagoras launch his argument, but then it is seen to be the thing in itself that exists absolutely speaking.
     From: comment on Protagoras (fragments/reports [c.441 BCE]) by José A. Benardete - Metaphysics: the logical approach Ch.8
If my hot wind is your cold wind, then wind is neither hot nor cold, and so not as cold as itself [Benardete,JA on Protagoras]
     Full Idea: Because the wind is cold to me but not you, Protagoras takes it to in itself neither cold nor not-cold. Accordingly, I very much doubt that he can allow the wind to be exactly as cold as itself.
     From: comment on Protagoras (fragments/reports [c.441 BCE]) by José A. Benardete - Metaphysics: the logical approach Ch.8
13. Knowledge Criteria / E. Relativism / 6. Relativism Critique
God is "the measure of all things", more than any man [Plato on Protagoras]
     Full Idea: In our view it is God who is pre-eminently the "measure of all things", much more so than any "man", as they say.
     From: comment on Protagoras (fragments/reports [c.441 BCE]) by Plato - The Laws 716c
Protagoras absurdly thought that the knowing or perceiving man is 'the measure of all things' [Aristotle on Protagoras]
     Full Idea: When Protagoras quipped that man is the measure of all things, he had in mind, of course, the knowing or perceiving man. The grounds are that they have perception/knowledge, and these are said to be the measures of objects. Utter nonsense!
     From: comment on Protagoras (fragments/reports [c.441 BCE]) by Aristotle - Metaphysics 1053b
Relativists think if you poke your eye and see double, there must be two things [Aristotle on Protagoras]
     Full Idea: In fact there is no difference between Protagoreanism and saying this: if you stick your finger under your eyes and make single things seem two, then they are two, just because they seem to be two.
     From: comment on Protagoras (fragments/reports [c.441 BCE]) by Aristotle - Metaphysics 1063a06
17. Mind and Body / E. Mind as Physical / 6. Conceptual Dualism
Analysing mental concepts points to 'inclusionism' - that mental phenomena are part of the physical [Jubien]
     Full Idea: We have (physicalist) 'inclusionism' when the mental is included in the physical, and mental phenomena are to be found among physical phenomena. Only inclusionism is compatible with a genuine physicalist analysis of mental concepts.
     From: Michael Jubien (Possibility [2009], 4.5)
     A reaction: This isn't the thesis of conceptual dualism (which I like), but an interesting accompaniment for it. Jubien is offering this as an alternative to 'reductive' analysis, translating all the mental concepts into physical language. He extends 'physical'.
19. Language / B. Reference / 3. Direct Reference / a. Direct reference
First-order logic tilts in favour of the direct reference theory, in its use of constants for objects [Jubien]
     Full Idea: First-order logic tilts in favor of the direct reference account of proper names by using individual constants to play the intuitive role of names, and by 'interpreting' the constants simply as the individuals that are assigned to them for truth-values.
     From: Michael Jubien (Possibility [2009], Intro)
     A reaction: This is the kind of challenge to orthodoxy that is much needed at the moment. We have an orthodoxy which is almost a new 'scholasticism', that logic will clarify our metaphysics. Trying to enhance the logic for the job may be a dead end.
22. Metaethics / A. Ethics Foundations / 2. Source of Ethics / j. Ethics by convention
Early sophists thought convention improved nature; later they said nature was diminished by it [Protagoras, by Miller,FD]
     Full Idea: Protagoras and Hippias evidently believed that convention was an improvement on nature, whereas later sophists such as Antiphon, Thrasymachus and Callicles seemed to contend that conventional morality was undermined because it was 'against nature'.
     From: report of Protagoras (fragments/reports [c.441 BCE]) by Fred D. Miller jr - Classical Political Thought
     A reaction: This gets to the heart of a much more interesting aspect of the nomos-physis (convention-nature) debate, rather than just a slanging match between relativists and the rest. The debate still goes on, over issues about the free market and intervention.
23. Ethics / B. Contract Ethics / 1. Contractarianism
For Protagoras the only bad behaviour is that which interferes with social harmony [Protagoras, by Roochnik]
     Full Idea: For Protagoras the only constraint on human behaviour is that it not interfere with social harmony, the essential condition for human survival.
     From: report of Protagoras (fragments/reports [c.441 BCE]) by David Roochnik - The Tragedy of Reason p.63
23. Ethics / C. Virtue Theory / 2. Elements of Virtue Theory / d. Teaching virtue
Protagoras contradicts himself by saying virtue is teachable, but then that it is not knowledge [Plato on Protagoras]
     Full Idea: Protagoras claimed that virtue was teachable, but now tries to show it is not knowledge, which makes it less likely to be teachable.
     From: comment on Protagoras (fragments/reports [c.441 BCE]) by Plato - Protagoras 361b
25. Social Practice / D. Justice / 3. Punishment / b. Retribution for crime
Protagoras seems to have made the huge move of separating punishment from revenge [Protagoras, by Vlastos]
     Full Idea: The distinction of punishment from revenge must be regarded as one of the most momentous of the conceptual discoveries ever made by humanity in the course of its slow, tortuous, precarious, emergence from barbaric tribalism. Protagoras originated it.
     From: report of Protagoras (fragments/reports [c.441 BCE]) by Gregory Vlastos - Socrates: Ironist and Moral Philosopher p.187
25. Social Practice / E. Policies / 5. Education / a. Aims of education
Successful education must go deep into the soul [Protagoras]
     Full Idea: Education does not take root in the soul unless one goes deep.
     From: Protagoras (fragments/reports [c.441 BCE], B11), quoted by Plutarch - On Practice 178.25
25. Social Practice / E. Policies / 5. Education / b. Education principles
He spent public money on education, as it benefits the individual and the state [Protagoras, by Diodorus of Sicily]
     Full Idea: He used legislation to improve the condition of illiterate people, on the grounds that they lack one of life's great goods, and thought literacy should be a matter of public concern and expense.
     From: report of Protagoras (fragments/reports [c.441 BCE]) by Diodorus of Sicily - Universal History 12.13.3.3
28. God / C. Attitudes to God / 5. Atheism
He said he didn't know whether there are gods - but this is the same as atheism [Diogenes of Oen. on Protagoras]
     Full Idea: He said that he did not know whether there were gods - but this is the same as saying that he knew there were no gods.
     From: comment on Protagoras (fragments/reports [c.441 BCE], A23) by Diogenes (Oen) - Wall inscription 11 Chil 2