15 ideas
| 9193 | ZF set theory has variables which range over sets, 'equals' and 'member', and extensionality [Dummett] |
| Full Idea: ZF set theory is a first-order axiomatization. Variables range over sets, there are no second-order variables, and primitive predicates are just 'equals' and 'member of'. The axiom of extensionality says sets with the same members are identical. | |
| From: Michael Dummett (The Philosophy of Mathematics [1998], 7) | |
| A reaction: If the eleven members of the cricket team are the same as the eleven members of the hockey team, is the cricket team the same as the hockey team? Our cricket team is better than our hockey team, so different predicates apply to them. |
| 9194 | The main alternative to ZF is one which includes looser classes as well as sets [Dummett] |
| Full Idea: The main alternative to ZF is two-sorted theories, with some variables ranging over classes. Classes have more generous existence assumptions: there is a universal class, containing all sets, and a class containing all ordinals. Classes are not members. | |
| From: Michael Dummett (The Philosophy of Mathematics [1998], 7.1.1) | |
| A reaction: My intuition is to prefer strict systems when it comes to logical theories. The whole point is precision. Otherwise we could just think about things, and skip all this difficult symbolic stuff. |
| 9195 | Intuitionists reject excluded middle, not for a third value, but for possibility of proof [Dummett] |
| Full Idea: It must not be concluded from the rejection of excluded middle that intuitionistic logic operates with three values: true, false, and neither true nor false. It does not make use of true and false, but only with a construction being a proof. | |
| From: Michael Dummett (The Philosophy of Mathematics [1998], 8.1) | |
| A reaction: This just sounds like verificationism to me, with all its problems. It seems to make speculative statements meaningless, which can't be right. Realism has lots of propositions which are assumed to be true or false, but also unknowable. |
| 9186 | First-order logic concerns objects; second-order adds properties, kinds, relations and functions [Dummett] |
| Full Idea: First-order logic is distinguished by generalizations (quantification) only over objects: second-order logic admits generalizations or quantification over properties or kinds of objects, and over relations between them, and functions defined over them. | |
| From: Michael Dummett (The Philosophy of Mathematics [1998], 3.1) | |
| A reaction: Second-order logic was introduced by Frege, but is (interestingly) rejected by Quine, because of the ontological commitments involved. I remain unconvinced that quantification entails ontological commitment, so I'm happy. |
| 9187 | Logical truths and inference are characterized either syntactically or semantically [Dummett] |
| Full Idea: There are two ways of characterizing logical truths and correct inference. Proof-theoretic or syntactic characterizations, if the formalization admits of proof or derivation; and model-theoretic or semantic versions, being true in all interpretations. | |
| From: Michael Dummett (The Philosophy of Mathematics [1998], 3.1) | |
| A reaction: Dummett calls this distinction 'fundamental'. The second one involves truth, and hence meaning, where the first one just responds to rules. ..But how can you have a notion of correctly following a rule, without a notion of truth? |
| 9191 | Ordinals seem more basic than cardinals, since we count objects in sequence [Dummett] |
| Full Idea: It can be argued that the notion of ordinal numbers is more fundamental than that of cardinals. To count objects, we must count them in sequence. ..The theory of ordinals forms the substratum of Cantor's theory of cardinals. | |
| From: Michael Dummett (The Philosophy of Mathematics [1998], 5) | |
| A reaction: Depends what you mean by 'fundamental'. I would take cardinality to be psychologically prior ('that is a lot of sheep'). You can't order people by height without first acquiring some people with differing heights. I vote for cardinals. |
| 9192 | The number 4 has different positions in the naturals and the wholes, with the same structure [Dummett] |
| Full Idea: The number 4 cannot be characterized solely by its position in a system, because it has different positions in the system of natural numbers and that of the positive whole numbers, whereas these systems have the very same structure. | |
| From: Michael Dummett (The Philosophy of Mathematics [1998], 6.1) | |
| A reaction: Dummett seems to think this is fairly decisive against structuralism. There is also the structure of the real numbers. We will solve this by saying that the wholes are abstracted from the naturals, which are abstracted from the reals. Job done. |
| 6375 | The taste of chocolate is a 'finer-grained' sensation than the taste of sweetness [Polger] |
| Full Idea: The taste of chocolate is presumably a 'finer-grained' sensation than the taste of sweetness. | |
| From: Thomas W. Polger (Natural Minds [2004], Ch.1.4) | |
| A reaction: An interesting distinction when it comes to what they are like, and whether two very different brains can realise them. Sweetness might be the same for most creatures, but the tast of chocolate subtly different. |
| 6381 | The mind and the self are one, and the mind-self is a biological phenomenon [Polger] |
| Full Idea: We should return to the old idea that the mind and the self are one and combine it with the new idea that the mind-self is a biological phenomenon. | |
| From: Thomas W. Polger (Natural Minds [2004], §8.3) | |
| A reaction: This doesn't make allowance for the fact that some parts of my mind seem like irritating visitors, and other parts seem like the home-owner. Personally I take the self to be the brain's central controller, or the centre (forum) of brain integration. |
| 6378 | Teleological functions explain why a trait exists; causal-role functions say what it does [Polger] |
| Full Idea: Teleological functions help explain why a trait has come to exist; causal-role functions tell what a trait does or is apt to do. | |
| From: Thomas W. Polger (Natural Minds [2004], §5.4) | |
| A reaction: The teleological view has the merit of nesting nicely with the theory of evolution, and with Aristotelian virtue ethics (which I like). Causal-role functionalism focuses better on what is actually happening inside the head. |
| 6380 | Identity theory says consciousness is an abstraction: a state, event, process or property [Polger] |
| Full Idea: Identity theories locate consciousness at a certain order of abstraction, typically among neurophysiological states, events, processes, or properties. | |
| From: Thomas W. Polger (Natural Minds [2004], Ch.7.6) | |
| A reaction: I increasingly think that processes are the answer. My new analogy for the mind is a waterfall: its physical ontology is simple, it only exists because there is a sustained process, and it is far too complex to predict individual droplet outcomes. |
| 22817 | Citizenship involves a group of mutually supporting rights, which create community and equality [Miller,D] |
| Full Idea: The idea of citizenship is that rights support each other. Protective and welfare rights provide a basis for a political role. This underpins a sense of membership, and an obligation to provide welfare. Rights confer equal status and self-respect. | |
| From: David Miller (Community and Citizenship [1989], 3) | |
| A reaction: A helpful eludation of what a richer concept of citizenship than mere membership might look like. Communitarians have a different concept of rights from that of liberals. |
| 22816 | Socialists reject nationality as a false source of identity [Miller,D] |
| Full Idea: The socialist tradition has been overwhelmingly hostile to nationality as a source of identity, usually regarding it merely as an artificially created impediment to the brotherhood of man. | |
| From: David Miller (Community and Citizenship [1989], 2) | |
| A reaction: I have some sympathy with this, especially when nationalism is expressed in terms of enemies, but the question of what community a person can plausibly identify with is difficult. We start in hunter gather tribes of several hundred. |
| 6379 | A mummified heart has the teleological function of circulating blood [Polger] |
| Full Idea: A preserved heart in a jar of formaldehyde has the teleological function of circulating blood. | |
| From: Thomas W. Polger (Natural Minds [2004], §5.4) | |
| A reaction: A nice illustration. |
| 6377 | Teleological notions of function say what a thing is supposed to do [Polger] |
| Full Idea: Teleological notions of function specify not just what a thing happens to do, but what it is supposed to do. | |
| From: Thomas W. Polger (Natural Minds [2004], Ch.5.3) | |
| A reaction: This is the basis of a distinct theory of the mind. It seems to be akin to the 'dispositions' of behaviourism, so that the mind becomes once more a theoretical and abstract entity, rather than a thing of occurrent events and processes. |