22 ideas
| 19066 | Philosophy aims to understand the world, through ordinary experience and science [Dummett] |
| Full Idea: Philosophy is an attempt to understand the world, as it is revealed to us both in our ordinary experience and by the discoveries and theories of science. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.311) | |
| A reaction: I don't see a sharp division between 'ordinary' and 'scientific'. I really like this idea, first because it makes 'understanding' central, and second because it wants both revelations. In discussing matter and time, there is too much emphasis on science. |
| 19067 | A successful proof requires recognition of truth at every step [Dummett] |
| Full Idea: For a demonstration to be cogent it is necessary that the passage from step to step involve a recognition of truth at each line. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.313) | |
| A reaction: Dummett cited Quine (esp. 1970) as having an almost entirely syntactic view of logic. Rumfitt points out that logic can move validly from one falsehood to another. Even a 'proof' might detour into falsehood, but it would not be a 'canonical' proof! |
| 19060 | Truth-tables are dubious in some cases, and may be a bad way to explain connective meaning [Dummett] |
| Full Idea: It is arguable whether two-valued truth tables give correct meanings for certain sentential operators, and even whether they constitute legitimate explanations of any possible sentential operators. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.294) | |
| A reaction: See 'Many-valued logic' for examples of non-binary truth tables. Presumably logicians should aspire to make their semantics precise, as well as their syntax. |
| 15163 | The interest of quantified modal logic is its metaphysical necessity and essentialism [Soames] |
| Full Idea: The chief philosophical interest in quantified modal logic lies with metaphysical necessity, essentialism, and the nontrivial modal de re. | |
| From: Scott Soames (Philosophy of Language [2010], 3.1) |
| 11066 | Deduction is justified by the semantics of its metalanguage [Dummett, by Hanna] |
| Full Idea: For Dummett the semantics of the metalanguage is the external and objective source of the justification of deduction. | |
| From: report of Michael Dummett (The Justification of Deduction [1973]) by Robert Hanna - Rationality and Logic 3.4 | |
| A reaction: This is offered as an answer to the Lewis Carroll problem that justifying deduction seems to need deduction, thus leading to a regress. [There is a reply to Dummett by Susan Haack] |
| 19058 | Syntactic consequence is positive, for validity; semantic version is negative, with counterexamples [Dummett] |
| Full Idea: A plausible account is that the syntactic notion of consequence is for positive results, that some form of argument is valid; the semantic notion is required for negative results, that some argument is invalid, because a counterexample can be found. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.292) | |
| A reaction: This rings true for the two strategies of demonstration, the first by following the rules in steps, the second by using your imagination (or a tableau) to think up problems. |
| 15158 | Indefinite descriptions are quantificational in subject position, but not in predicate position [Soames] |
| Full Idea: The indefinite description in 'A man will meet you' is naturally treated as quantificational, but an occurrence in predicative position, in 'Jones is not a philosopher', doesn't have a natural quantificational counterpart. | |
| From: Scott Soames (Philosophy of Language [2010], 1.23) |
| 15157 | Recognising the definite description 'the man' as a quantifier phrase, not a singular term, is a real insight [Soames] |
| Full Idea: Recognising the definite description 'the man' as a quantifier phrase, rather than a singular term, is a real insight. | |
| From: Scott Soames (Philosophy of Language [2010], 1.22) | |
| A reaction: 'Would the man who threw the stone come forward' seems like a different usage from 'would the man in the black hat come forward'. |
| 15156 | The universal and existential quantifiers were chosen to suit mathematics [Soames] |
| Full Idea: Since Frege and Russell were mainly interested in formalizing mathematics, the only quantifiers they needed were the universal and existential one. | |
| From: Scott Soames (Philosophy of Language [2010], 1.22) |
| 19063 | Beth trees show semantics for intuitionistic logic, in terms of how truth has been established [Dummett] |
| Full Idea: Beth trees give a semantics for intuitionistic logic, by representing sentence meaning in terms of conditions under which it is recognised to have been established as true. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.305) |
| 19059 | In standard views you could replace 'true' and 'false' with mere 0 and 1 [Dummett] |
| Full Idea: Nothing is lost, on this view, if in the standard semantic treatment of classical sentential logic, we replace the standard truth-values 'true' and 'false' by the numbers 0 and 1. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.294) | |
| A reaction: [A long context will explain 'on this view'] He is discussing the relationship of syntactic and semantic consequence, and goes on to criticise simple binary truth-table accounts of connectives. Semantics on a computer would just be 0 and 1. |
| 19062 | Classical two-valued semantics implies that meaning is grasped through truth-conditions [Dummett] |
| Full Idea: The standard two-valued semantics for classical logic involves a conception under which to grasp the meaning of a sentence is to apprehend the conditions under which it is, or is not, true. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.305) | |
| A reaction: The idea is that you only have to grasp the truth tables for sentential logic, and that needs nothing more than knowing whether a sentence is true or false. I'm not sure where the 'conditions' creep in, though. |
| 19065 | Soundness and completeness proofs test the theory of meaning, rather than the logic theory [Dummett] |
| Full Idea: A proof of soundess or completeness is a test, not so much of the logical theory to which it applies, but of the theory of meaning which underlies the semantics. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.310) | |
| A reaction: These two types of proof concern how the syntax and the semantics match up, so this claim sounds plausible, though I tend to think of them as more like roadworthiness tests for logic, checking how well they function. |
| 15161 | There are more metaphysically than logically necessary truths [Soames] |
| Full Idea: The set of metaphysically necessary truths is larger than the set of logically necessary truths. | |
| From: Scott Soames (Philosophy of Language [2010], 3.1) | |
| A reaction: Likewise, the set of logically possible truths is much larger than the set of metaphysically possible truths. If a truth is logically necessary, it will clearly be metaphysically necessary. Er, unless it is necessitated by daft logic... |
| 15162 | We understand metaphysical necessity intuitively, from ordinary life [Soames] |
| Full Idea: Our understanding of metaphysical necessity is intuitive - drawn from our ordinary thought and talk. | |
| From: Scott Soames (Philosophy of Language [2010], 3.1) | |
| A reaction: This, of course, is a good reason for analytic philosophers to dislike metaphysical necessity. |
| 19061 | An explanation is often a deduction, but that may well beg the question [Dummett] |
| Full Idea: An explanation is often a deductive argument, with the fact needing explaining as its conclusion. ...But the conclusion is usually given in advance, and we may only believe the premisses because they plausibly explain the conclusion. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.296) | |
| A reaction: [compressed (Dummett's wordy prose cries out for it!)] I suppose this works better in mathematics, which is central to Dummett's interests. In the real world the puzzle is not usually logically implied by its explanation. |
| 15152 | To study meaning, study truth conditions, on the basis of syntax, and representation by the parts [Soames] |
| Full Idea: The systematic study of meaning requires a framework for specifying the truth conditions of sentences on the basis of their syntactic structure, and the representational contents of their parts. | |
| From: Scott Soames (Philosophy of Language [2010], Intro) | |
| A reaction: Soames presents this as common sense, on the first page of his book, and it is hard to disagree. Representation will shade off into studying the workings of the mind. Fodor seems a good person to start with. |
| 15153 | Tarski's account of truth-conditions is too weak to determine meanings [Soames] |
| Full Idea: The truth conditions provided by Tarski's theories (based on references of subsentential constituents) are too weak to determine meanings, because they lacked context-sensitivity and various forms of intensionality. | |
| From: Scott Soames (Philosophy of Language [2010], Intro) | |
| A reaction: Interesting. This suggests that stronger modern axiomatic theories of truth might give a sufficient basis for a truth conditions theory of meaning. Soames says possible worlds semantics was an attempt to improve things. |
| 19064 | Holism is not a theory of meaning; it is the denial that a theory of meaning is possible [Dummett] |
| Full Idea: In the sense of giving a model for the content of a sentence, its representative power, holism is not a theory of meaning; it is the denial that a theory of meaning is possible. | |
| From: Michael Dummett (The Justification of Deduction [1973], p.309) | |
| A reaction: This will obviously be because sentences just don't have meaning in isolation, so their meaning can't be given in terms of the sentences. |
| 15154 | We should use cognitive states to explain representational propositions, not vice versa [Soames] |
| Full Idea: Instead of explaining the representationality of sentences and cognitive states in terms of propositions, we must explain the representationality of propositions in terms of the representationality of the relevant cognitive states. | |
| From: Scott Soames (Philosophy of Language [2010], Intro) | |
| A reaction: Music to my ears. I am bewildered by this Russellian notion of a 'proposition' as some abstract entity floating around in the world waiting to be expressed. The vaguer word 'facts' (and false facts?) will cover that. It's Frege's fault. |
| 16713 | Philosophers are the forefathers of heretics [Tertullian] |
| Full Idea: Philosophers are the forefathers of heretics. | |
| From: Tertullian (works [c.200]), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 20.2 |
| 6610 | I believe because it is absurd [Tertullian] |
| Full Idea: I believe because it is absurd ('Credo quia absurdum est'). | |
| From: Tertullian (works [c.200]), quoted by Robert Fogelin - Walking the Tightrope of Reason n4.2 | |
| A reaction: This seems to be a rather desperate remark, in response to what must have been rather good hostile arguments. No one would abandon the support of reason if it was easy to acquire. You can't deny its engaging romantic defiance, though. |