19 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. |
| 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. |
| 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. |
| 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. |
| 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. |
| 7602 | In the Bible God changes his mind (repenting of creating humanity, in the Flood) [Armstrong,K] |
| Full Idea: In the Bible God changes his mind, as when he repents of having made man and decides to destroy the human race in the Flood. | |
| From: Karen Armstrong (A History of God [1993], Ch.1) | |
| A reaction: It becomes apparent that the most startling feature of Christian fundamentalism is its uncritical reading of the Bible, in which passages are wilfully lifted from context, and inconvenient inconsistencies are ruthlessly ignored. |
| 7605 | Monotheism introduced intolerance into religious thinking [Armstrong,K] |
| Full Idea: We have become so used to the intolerance of monotheism that we may not appreciate that its hostility towards other gods was a new religious attitude; paganism was an essentially tolerant faith. | |
| From: Karen Armstrong (A History of God [1993], Ch.2) | |
| A reaction: The comedian Dave Allen always signed off with "may your god go with you". To me the most striking feature of monotheists is frequently their barely controlled aggression, beneath a mask of strained compassion. |
| 7599 | Around 800 BCE teachers superseded gods in India [Armstrong,K] |
| Full Idea: Around the eighth century BCE the gods ceased to be very important in India, and would be superseded by the religious teacher, who would be considered higher than the gods. | |
| From: Karen Armstrong (A History of God [1993], Ch.1) | |
| A reaction: At least there has been one culture that gave an appropriate status to teachers. It seems astonishing in that age that human beings could have higher status than gods - way before the European 'humanists'. |
| 7597 | There is virtually no sign of monotheism in the Pentateuch [Armstrong,K] |
| Full Idea: It is very difficult to find a single monotheistic statement in the whole of the Pentateuch, and even the Ten Commandments take the existence of other gods for granted ("There shall be no strange gods for you before my face"). | |
| From: Karen Armstrong (A History of God [1993], Ch.1) | |
| A reaction: The transition from polytheism to monotheism is very strange. First God is 'jealous' of other gods, then supremely above them, and eventually totally exclusive. It's like watching the rise of Stalin. |
| 7606 | The idea that Jesus was God was only settled in the fourth century [Armstrong,K] |
| Full Idea: Jesus himself certainly never claimed to be God, and the doctrine that Jesus had been God in human form was not finalised until the fourth century. | |
| From: Karen Armstrong (A History of God [1993], Ch.3) | |
| A reaction: It was this final view which seems to have provoked Muhammed into developing a religion with the slogan "there is only one God". In Christianity an initially promising set of teachings grew into a prolonged irrational hysteria. |
| 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 |
| 7596 | Faith is not just belief in propositions, but also putting trust in them [Armstrong,K] |
| Full Idea: There is a distinction between belief in a set of propositions and a faith which enables us to put our trust in them. | |
| From: Karen Armstrong (A History of God [1993], Intro) | |
| A reaction: This is interestingly distinct from the usual idea that faith is putting belief in propositions which are not sufficiently rationally justified. How many philosophers actually have faith in the propositions they say they believe? |
| 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. |