29 ideas
| 10751 | Second-order logic needs the sets, and its consequence has epistemological problems [Rossberg] |
| Full Idea: Second-order logic raises doubts because of its ontological commitment to the set-theoretic hierarchy, and the allegedly problematic epistemic status of the second-order consequence relation. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §1) | |
| A reaction: The 'epistemic' problem is whether you can know the truths, given that the logic is incomplete, and so they cannot all be proved. Rossberg defends second-order logic against the second problem. A third problem is that it may be mathematics. |
| 10757 | Henkin semantics has a second domain of predicates and relations (in upper case) [Rossberg] |
| Full Idea: Henkin semantics (for second-order logic) specifies a second domain of predicates and relations for the upper case constants and variables. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: This second domain is restricted to predicates and relations which are actually instantiated in the model. Second-order logic is complete with this semantics. Cf. Idea 10756. |
| 10759 | There are at least seven possible systems of semantics for second-order logic [Rossberg] |
| Full Idea: In addition to standard and Henkin semantics for second-order logic, one might also employ substitutional or game-theoretical or topological semantics, or Boolos's plural interpretation, or even a semantics inspired by Lesniewski. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: This is helpful in seeing the full picture of what is going on in these logical systems. |
| 10753 | Logical consequence is intuitively semantic, and captured by model theory [Rossberg] |
| Full Idea: Logical consequence is intuitively taken to be a semantic notion, ...and it is therefore the formal semantics, i.e. the model theory, that captures logical consequence. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §2) | |
| A reaction: If you come at the issue from normal speech, this seems right, but if you start thinking about the necessity of logical consequence, that formal rules and proof-theory seem to be the foundation. |
| 10752 | Γ |- S says S can be deduced from Γ; Γ |= S says a good model for Γ makes S true [Rossberg] |
| Full Idea: Deductive consequence, written Γ|-S, is loosely read as 'the sentence S can be deduced from the sentences Γ', and semantic consequence Γ|=S says 'all models that make Γ true make S true as well'. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §2) | |
| A reaction: We might read |= as 'true in the same model as'. What is the relation, though, between the LHS and the RHS? They seem to be mutually related to some model, but not directly to one another. |
| 10754 | In proof-theory, logical form is shown by the logical constants [Rossberg] |
| Full Idea: A proof-theorist could insist that the logical form of a sentence is exhibited by the logical constants that it contains. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §2) | |
| A reaction: You have to first get to the formal logical constants, rather than the natural language ones. E.g. what is the truth table for 'but'? There is also the matter of the quantifiers and the domain, and distinguishing real objects and predicates from bogus. |
| 4568 | If 'Queen of England' does not refer if there is no queen, its meaning can't refer if there is one [Cooper,DE] |
| Full Idea: If 'the Queen of England' is not a referring expression when there is no queen, nor can it be one when there is a queen - since the meaning of the expression is the same in either case. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §4.1) | |
| A reaction: I'm not convinced. Does this mean that since I can point with my finger at nothing, I therefore do not indicate anything when there is an object at which I am pointing. Sounds silly to me. |
| 10756 | A model is a domain, and an interpretation assigning objects, predicates, relations etc. [Rossberg] |
| Full Idea: A standard model is a set of objects called the 'domain', and an interpretation function, assigning objects in the domain to names, subsets to predicate letters, subsets of the Cartesian product of the domain with itself to binary relation symbols etc. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: The model actually specifies which objects have which predicates, and which objects are in which relations. Tarski's account of truth in terms of 'satisfaction' seems to be just a description of those pre-decided facts. |
| 10758 | If models of a mathematical theory are all isomorphic, it is 'categorical', with essentially one model [Rossberg] |
| Full Idea: A mathematical theory is 'categorical' if, and only if, all of its models are isomorphic. Such a theory then essentially has just one model, the standard one. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: So the term 'categorical' is gradually replacing the much-used phrase 'up to isomorphism'. |
| 10761 | Completeness can always be achieved by cunning model-design [Rossberg] |
| Full Idea: All that should be required to get a semantics relative to which a given deductive system is complete is a sufficiently cunning model-theorist. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §5) |
| 10755 | A deductive system is only incomplete with respect to a formal semantics [Rossberg] |
| Full Idea: No deductive system is semantically incomplete in and of itself; rather a deductive system is incomplete with respect to a specified formal semantics. | |
| From: Marcus Rossberg (First-order Logic, 2nd-order, Completeness [2004], §3) | |
| A reaction: This important point indicates that a system might be complete with one semantics and incomplete with another. E.g. second-order logic can be made complete by employing a 'Henkin semantics'. |
| 4574 | If some peoples do not have categories like time or cause, they can't be essential features of rationality [Cooper,DE] |
| Full Idea: If our most basic concepts, like time, space, substance or causality, are not shared by some peoples, it puts paid to the cherished ideal of philosophers to discover a set of concepts or categories which any rational human must employ in his thinking. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §5.2) | |
| A reaction: This seems to be a place where a priori philosophy (Aristotle,Kant,Hegel) meets empirical research (Whorf). However, interpreting the research is so fraught with problems it drives you back to the a priori… |
| 7301 | The phenomenalist says that to be is to be perceivable [Cardinal/Hayward/Jones] |
| Full Idea: Where the idealist says that to be (i.e. to exist) is to be perceived, the phenomenalist says that to be is to be perceivable. | |
| From: Cardinal/Hayward/Jones (Epistemology [2004], Ch.4) | |
| A reaction: This is a nice phenomenalist slogan to add to Mill's well known one (Idea 3583). Expressed in this form, it looks false to me. What about neutrinoes? They weren't at all perceivable until recently. Maybe some physical stuff can never be perceived. |
| 7302 | Linguistic phenomenalism says we can eliminate talk of physical objects [Cardinal/Hayward/Jones] |
| Full Idea: Linguistic phenomenalism argues that it is possible to remove all talk of physical objects from our speech with no loss of meaning. | |
| From: Cardinal/Hayward/Jones (Epistemology [2004], Ch.4) | |
| A reaction: I find this proposal unappealing. My basic objection is that I cannot understand why anyone would refuse to even contemplate the question of WHY I am having a given group of consistent experiences, of (say) a table kind. |
| 7303 | If we lack enough sense-data, are we to say that parts of reality are 'indeterminate'? [Cardinal/Hayward/Jones] |
| Full Idea: The problem with taking sense-data as basic is that some data can appear indeterminate. If we can't discern the colour of someone's eyes, or the number of sides of a complex figure, are we to say that there is no fact about those things? | |
| From: Cardinal/Hayward/Jones (Epistemology [2004], Ch.4) | |
| A reaction: I like that. How many electrons are there in the sun? Such things cannot just be reduced to talk of sense-data, as there is obviously a vast gap between the data and the facts. As usual, ontology and epistemology must be kept separate. |
| 7299 | Primary qualities can be described mathematically, unlike secondary qualities [Cardinal/Hayward/Jones] |
| Full Idea: All the primary qualities lend themselves readily to mathematical or geometric description. ...but it seems that secondary qualities are less amenable to being represented mathematically. | |
| From: Cardinal/Hayward/Jones (Epistemology [2004], Ch.4) | |
| A reaction: As a believer in the primary/secondary distinction, I welcome this point. This is either evidence for the external reality of primary qualities, or an interesting observation about maths. Do we make the primary/secondary distinction because we do maths? |
| 7300 | An object cannot remain an object without its primary qualities [Cardinal/Hayward/Jones] |
| Full Idea: An object cannot lack shape, size, position or motion and remain an object. | |
| From: Cardinal/Hayward/Jones (Epistemology [2004], Ch.4) | |
| A reaction: This points towards the essentialist view (see Idea 5453). This does raise the question of whether an object could lose its colour with impugnity, or the quality of sound that it makes when struck. |
| 7297 | My justifications might be very coherent, but totally unconnected to the world [Cardinal/Hayward/Jones] |
| Full Idea: My beliefs could be well justified in coherentist terms, while not accurately representing the world, and my system of beliefs could be completely free-floating. | |
| From: Cardinal/Hayward/Jones (Epistemology [2004], Ch.3) | |
| A reaction: This nicely encapsulates to correspondence objection to coherence theory. One thing missing from the coherence account is that beliefs aren't chosen for their coherence, but are mostly unthinkingly triggered by experiences. |
| 4573 | If it is claimed that language correlates with culture, we must be able to identify the two independently [Cooper,DE] |
| Full Idea: If it is claimed that linguistic differences significantly correlate with cultural differences, it must therefore be possible to identify the linguistic differences independently from the cultural ones. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §5.1) | |
| A reaction: This is a basic objection to any extreme relativist version of the S-P hypothesis. They are part of the conspiracy to overemphasise language in philosophy, and they are wrong. |
| 4575 | A person's language doesn't prove their concepts, but how are concepts deduced apart from language? [Cooper,DE] |
| Full Idea: It would be absurd to say the Hopi lack the concept of time because they lack tensed verbs, ..but how do we find out what a man's concepts are except in terms of his language? | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §5.2) | |
| A reaction: Presumably we should look at animals, where concepts must be inferred in order to explain behaviour. I don't see why introspection (scientifically wicked) should not also be employed to detect our own non-verbal concepts. How are new words invented? |
| 4561 | Many sentences set up dispositions which are irrelevant to the meanings of the sentences [Cooper,DE] |
| Full Idea: Many sentences set up dispositions which are irrelevant to the meanings of the sentences. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §2.3) | |
| A reaction: Yet another telling objection to behaviourism. When I look at broccoli I may have a disposition to be sick, but that isn't part of the concept of broccoli. |
| 4564 | I can meaningfully speculate that humans may have experiences currently impossible for us [Cooper,DE] |
| Full Idea: It is not meaningless for me to postulate the potential for humans to sense in a manner which is at present unimaginable and indescribable. There is no reason to believe me, but I might be right. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §3.1) | |
| A reaction: The key counterexample to verificationist theories of meaning is wild speculations, which are clearly meaningful, though frequently far beyond any likely human experience. Logical positivists are allergic to imagination. |
| 4565 | The verification principle itself seems neither analytic nor verifiable [Cooper,DE] |
| Full Idea: It seems that the positivists must admit that there is at least one statement which is meaningful, but which is neither verifiable nor analytic - namely, the statement of the principle of verification itself. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §3.1) | |
| A reaction: Some people think this objection is decisive, but I think any theory must be permitted a few metatheoretic assertions or axioms which are beyond discussion. Ayer thought the VP might be treated as analytic. Everyone has to start somewhere. |
| 4562 | Most people know how to use the word "Amen", but they do not know what it means [Cooper,DE] |
| Full Idea: Most people know how to use the word "Amen", but they do not know what it means. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §2.4) | |
| A reaction: Personally I find examples like this decisive against the 'use' theory of meaning. Maybe the defence is that the theory works for sentences, and individual words (like passwords) are peripheral. |
| 4563 | 'How now brown cow?' is used for elocution, but this says nothing about its meaning [Cooper,DE] |
| Full Idea: The sentence 'How now brown cow?' has its use in elocutions classes, yet this aspect of its use tells us nothing about its meaning. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §2.4) | |
| A reaction: Indeed, and also there are weird sentence of which we can assemble a meaning, but cannot think of any conceivable use ('rats swim in purple marmalade'). |
| 4571 | Reference need not be a hit-or-miss affair [Cooper,DE] |
| Full Idea: Reference need not be a hit-or-miss affair. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §4.2) | |
| A reaction: Sounds right. If the basic scenario is picking someone out in a crowd, your listener may think they know which person you are talking about, with a high degree of probability. |
| 4566 | Any thesis about reference is also a thesis about what exists to be referred to [Cooper,DE] |
| Full Idea: Any thesis about reference is also going to be a thesis about what there is in existence to refer to. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §4) | |
| A reaction: I see the point, but we must not put the cart before the horse. I may have an intuition that something exists, but not know how to refer to it (because of my small vocabulary). |
| 4572 | If predicates name things, that reduces every sentence to a mere list of names [Cooper,DE] |
| Full Idea: If predicates are names of entities, then subject/predicate sentences are pairs of names, since subjects are names (or referring expressions). But a pair of names is not a sentence at all, it is a mere list. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §4.4) | |
| A reaction: If that is meant to demolish universals it is too quick. Concatenating names is not the same as listing them. A relationship is asserted. There is a (mysterious) Platonic 'partaking' between form and particular. Perhaps. |
| 4576 | An analytic truth is one which becomes a logical truth when some synonyms have been replaced [Cooper,DE] |
| Full Idea: The definition of analytic truth which has, I believe, the most chance of success is one in terms of synonymy; ..an analytic truth is one which can be transformed into a logical truth once synonyms are replaced by synonyms. | |
| From: David E. Cooper (Philosophy and the Nature of Language [1973], §7.1) | |
| A reaction: Sounds promising, though there is Quine's notorious problem of circularity in all these concepts. If synonymy is conventional, then so is analyticity. I personally feel that the circle can be broken. |