22 ideas
| 18951 | For scientific purposes there is a precise concept of 'true-in-L', using set theory [Putnam] |
| Full Idea: For a language L there is a predicate 'true-in-L' which one can employ for all scientific purposes in place of intuitive truth, and this predicate admits of a precise definition using only the vocabulary of L itself plus set theory. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.2) | |
| A reaction: He refers, of course, to Tarski's theory. I'm unclear of the division between 'scientific purposes' and the rest of life (which is why some people embrace 'minimal' theories of ordinary truth). I'm struck by set theory being a necessary feature. |
| 18953 | Modern notation frees us from Aristotle's restriction of only using two class-names in premises [Putnam] |
| Full Idea: In modern notation we can consider potential logical principles that Aristotle never considered because of his general practice of looking at inferences each of whose premises involved exactly two class-names. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: Presumably you can build up complex inferences from a pair of terms, just as you do with pairs in set theory. |
| 18949 | The universal syllogism is now expressed as the transitivity of subclasses [Putnam] |
| Full Idea: On its modern interpretation, the validity of the inference 'All S are M; All M are P; so All S are P' just expresses the transitivity of the relation 'subclass of'. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.1) | |
| A reaction: A simple point I've never quite grasped. Since lots of syllogisms can be expressed as Venn Diagrams, in which the circles are just sets, it's kind of obvious really. So why does Sommers go back to 'terms'? See 'Term Logic'. |
| 18952 | '⊃' ('if...then') is used with the definition 'Px ⊃ Qx' is short for '¬(Px & ¬Qx)' [Putnam] |
| Full Idea: The symbol '⊃' (read 'if...then') is used with the definition 'Px ⊃ Qx' ('if Px then Qx') is short for '¬(Px & ¬Qx)'. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: So ⊃ and → are just abbreviations, and not really a proper part of the language. Notoriously, though, this is quite a long way from what 'if...then' means in ordinary English, and it leads to paradoxical oddities. |
| 18958 | In type theory, 'x ∈ y' is well defined only if x and y are of the appropriate type [Putnam] |
| Full Idea: In the theory of types, 'x ∈ y' is well defined only if x and y are of the appropriate type, where individuals count as the zero type, sets of individuals as type one, sets of sets of individuals as type two. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.6) |
| 18954 | Before the late 19th century logic was trivialised by not dealing with relations [Putnam] |
| Full Idea: It was essentially the failure to develop a logic of relations that trivialised the logic studied before the end of the nineteenth century. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: De Morgan, Peirce and Frege were, I believe, the people who put this right. |
| 18956 | Asserting first-order validity implicitly involves second-order reference to classes [Putnam] |
| Full Idea: The natural understanding of first-order logic is that in writing down first-order schemata we are implicitly asserting their validity, that is, making second-order assertions. ...Thus even quantification theory involves reference to classes. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: If, as a nominalist, you totally rejected classes, presumably you would get by in first-order logic somehow. To say 'there are no classes so there is no logical validity' sounds bonkers. |
| 18962 | Unfashionably, I think logic has an empirical foundation [Putnam] |
| Full Idea: Today, the tendency among philosophers is to assume that in no sense does logic itself have an empirical foundation. I believe this tendency is wrong. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.9) | |
| A reaction: I agree, not on the basis of indispensability to science, but on the basis of psychological processes that lead from experience to logic. Russell and Quine are Putnam's allies here, and Frege is his opponent. Putnam developed a quantum logic. |
| 18961 | We can identify functions with certain sets - or identify sets with certain functions [Putnam] |
| Full Idea: Instead of identifying functions with certain sets, I might have identified sets with certain functions. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.9) |
| 18955 | Having a valid form doesn't ensure truth, as it may be meaningless [Putnam] |
| Full Idea: I don't think all substitution-instances of a valid schema are 'true'; some are clearly meaningless, such as 'If all boojums are snarks and all snarks are egglehumphs, then all boojums are egglehumphs'. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.3) | |
| A reaction: This seems like a very good challenge to Quine's claim that it is only form which produces a logical truth. Keep deductive and semantic consequence separate, with two different types of 'logical truth'. |
| 18959 | Sets larger than the continuum should be studied in an 'if-then' spirit [Putnam] |
| Full Idea: Sets of a very high type or very high cardinality (higher than the continuum, for example) should today be investigated in an 'if-then' spirit. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.7) | |
| A reaction: This attitude goes back to Hilbert, but it fits with Quine's view of what is indispensable for science. It is hard to see a reason for the cut-off, just looking at the logic of expanding sets. |
| 1630 | We can only see an alien language in terms of our own thought structures (e.g. physical/abstract) [Quine] |
| Full Idea: We are prone to talk about physical and abstract objects. It is hard to know how else to talk, because we are bound to adapt any alien pattern to our own in the very process of understanding or translating the alien sentences. | |
| From: Willard Quine (Speaking of Objects [1960], pt.I,p.1) | |
| A reaction: It is fine for mathematicians (or economists) to refer to their subject matter as 'objects', but ontologists really need to be more careful. Some very silly theories can otherwise result. |
| 5747 | "No entity without identity" - our ontology must contain items with settled identity conditions [Quine, by Melia] |
| Full Idea: Quine's well-known slogan "no entity without identity" means that no object should be admitted into our ontology unless its identity conditions, the conditions that say which object it is, have been settled. | |
| From: report of Willard Quine (Speaking of Objects [1960]) by Joseph Melia - Modality Ch.4 | |
| A reaction: This invites science fiction scenarios, where we admit the existence of something before we have a clue what it is (whether it is physical, hallucination, divine..). Quine's slogan seems attractive but optimistic. How 'settled'? |
| 7925 | There is no proper identity concept for properties, and it is hard to distinguish one from two [Quine] |
| Full Idea: The lack of a proper identity concept for attributes (properties) is a lack that philosophers feel impelled to supply; for, what sense is there in saying there are attributes when there is no sense in saying when there is one attribute and when two? | |
| From: Willard Quine (Speaking of Objects [1960], IV) | |
| A reaction: This strikes me as being a really crucial question. There is a mistaken tendency to take any possible linguistic predicate as implying a natural property. I sympathise with the sceptics here (see Ideas 4029, 3906, 3322). How to individuate properties? |
| 18957 | Nominalism only makes sense if it is materialist [Putnam] |
| Full Idea: Nominalists must at heart be materialists, or so it seems to me: otherwise their scruples are unintelligible. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.5) | |
| A reaction: This is modern nominalism - the rejection of abstract objects. I largely plead guilty to both charges. |
| 13387 | Our conceptual scheme becomes more powerful when we posit abstract objects [Quine] |
| Full Idea: There is no denying the access of power that accrues to our conceptual scheme through the positing of abstract objects. | |
| From: Willard Quine (Speaking of Objects [1960], §5) | |
| A reaction: This seems right, both in its use of the word 'posit', and in its general pragmatic claim. So why? If they enable us to grapple with the world better, it must be because of their power of generalisation. They are nets thrown over chunks of reality. |
| 18950 | Physics is full of non-physical entities, such as space-vectors [Putnam] |
| Full Idea: Physics is full of references to such 'non-physical' entities as state-vectors, Hamiltonians, Hilbert space etc. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.2) | |
| A reaction: I take these to be concepts which are 'abstracted' from the physical facts, and so they don't strike me as being much of an ontological problem, or an objection to nominalism (which Putnam takes them to be). |
| 8277 | I prefer 'no object without identity' to Quine's 'no entity without identity' [Lowe on Quine] |
| Full Idea: To adapt Quine's famous slogan ('no entity without identity'), I prefer to say 'no object without identity'. | |
| From: comment on Willard Quine (Speaking of Objects [1960], p.52) by E.J. Lowe - The Possibility of Metaphysics 7.1 | |
| A reaction: Quine was trying to make us all more scientific, but Lowe is closer to common sense. The sky is an entity, most of us would say, but with very shaky identity-conditions. A wave of the sea is a good example. |
| 18960 | Most predictions are uninteresting, and are only sought in order to confirm a theory [Putnam] |
| Full Idea: Scientists want successful predictions in order to confirm their theories; they do not want theories in order to obtain the predictions, which are in some cases of not the slightest interest in themselves. | |
| From: Hilary Putnam (Philosophy of Logic [1971], Ch.8) | |
| A reaction: Equally, we might only care about the prediction, and have no interest at all in the theory. Farmers want weather predictions, not a PhD in meteorology. |
| 19216 | Propositions (such as 'that dog is barking') only exist if their items exist [Williamson] |
| Full Idea: A proposition about an item exists only if that item exists... how could something be the proposition that that dog is barking in circumstances in which that dog does not exist? | |
| From: Timothy Williamson (Necessary Existents [2002], p.240), quoted by Trenton Merricks - Propositions | |
| A reaction: This is a view of propositions I can't make sense of. If I'm under an illusion that there is a dog barking nearby, when there isn't one, can I not say 'that dog is barking'? If I haven't expressed a proposition, what have I done? |
| 1632 | Translation of our remote past or language could be as problematic as alien languages [Quine] |
| Full Idea: Translation of our remote past or future discourse into the terms we now know could be about as tenuous and arbitrary a projection as translation of a heathen language was seen to be. | |
| From: Willard Quine (Speaking of Objects [1960], pt.V,p.25) | |
| A reaction: Is he seriously saying that we can't understand Shakespeare, because holism implies that we would have to be Elizabethans? So scholarship is in vain? Is yesterday the 'past'? |
| 1631 | You could know the complete behavioural conditions for a foreign language, and still not know their beliefs [Quine] |
| Full Idea: We could know the necessary and sufficient stimulatory conditions of every possible act of utterance, in a foreign language, and still not know how to determine what objects the speakers of that language believe in. | |
| From: Willard Quine (Speaking of Objects [1960], pt.III,p.11) | |
| A reaction: I just don't believe this, because the same scepticism then creeps into discussions of native speakers of a single language, and all communcation is blighted - which is nonsense. |