31 ideas
| 7493 | Let us reason together, saith the Lord [Isaiah] |
| Full Idea: Come now, and let us reason together, saith the Lord. | |
| From: Isaiah (23: Book of Isaiah [c.680 BCE], 01.18) | |
| A reaction: A verse which not only offers Biblical support for philosophy, but would also seem to be a challenge to Christian fideists. |
| 17651 | Without words or other symbols, we have no world [Goodman] |
| Full Idea: We can have words without a world but no world without words or other symbols. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.3) | |
| A reaction: Goodman seems to have a particularly extreme version of the commitment to philosophy as linguistic. Non-human animals have no world, it seems. |
| 17652 | Truth is irrelevant if no statements are involved [Goodman] |
| Full Idea: Truth pertains solely to what is said ...For nonverbal versions and even for verbal versions without statements, truth is irrelevant. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.5) | |
| A reaction: Goodman is a philosopher of language (like Dummett), but I am a philosopher of thought (like Evans). The test, for me, is whether truth is applicable to the thought of non-human animals. I take it to be obvious that it is applicable. |
| 7786 | Propositional logic handles negation, disjunction, conjunction; predicate logic adds quantifiers, predicates, relations [Girle] |
| Full Idea: Propositional logic can deal with negation, disjunction and conjunction of propositions, but predicate logic goes beyond it to deal with quantifiers, predicates and relations. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 1.1) | |
| A reaction: This is on the first page of an introduction to the next stage, which is to include modal notions like 'must' and 'possibly'. |
| 7798 | There are three axiom schemas for propositional logic [Girle] |
| Full Idea: The axioms of propositional logic are: A→(B→A); A→(B→C)→(A→B)→(A→C) ; and (¬A→¬B)→(B→A). | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 6.5) |
| 7799 | Proposition logic has definitions for its three operators: or, and, and identical [Girle] |
| Full Idea: The operators of propositional logic are defined as follows: 'or' (v) is not-A implies B; 'and' (ampersand) is not A-implies-not-B; and 'identity' (three line equals) is A-implies-B and B-implies-A. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 6.5) |
| 7797 | Axiom systems of logic contain axioms, inference rules, and definitions of proof and theorems [Girle] |
| Full Idea: An axiom system for a logic contains three elements: a set of axioms; a set of inference rules; and definitions for proofs and theorems. There are also definitions for the derivation of conclusions from sets of premises. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 6.5) |
| 7794 | There are seven modalities in S4, each with its negation [Girle] |
| Full Idea: In S4 there are fourteen modalities: no-operator; necessarily; possibly; necessarily-possibly; possibly-necessarily; necessarily-possibly-necessarily; and possibly-necessarily-possibly (each with its negation). | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 3.5) | |
| A reaction: This is said to be 'more complex' than S5, but also 'weaker'. |
| 7793 | ◊p → □◊p is the hallmark of S5 [Girle] |
| Full Idea: The critical formula that distinguishes S5 from all others is: ◊p → □◊p. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 3.3) | |
| A reaction: If it is possible that it is raining, then it is necessary that it is possible that it is raining. But if it is possible in this world, how can that possibility be necessary in all possible worlds? |
| 7795 | S5 has just six modalities, and all strings can be reduced to those [Girle] |
| Full Idea: In S5 there are six modalities: no-operator; necessarily; and possibly (and their negations). In any sequence of operators we may delete all but the last to gain an equivalent formula. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 3.5) | |
| A reaction: Such drastic simplification seems attractive. Is there really no difference, though, between 'necessarily-possibly', 'possibly-possibly' and just 'possibly'? Could p be contingently possible in this world, and necessarily possible in another? |
| 7787 | Possible worlds logics use true-in-a-world rather than true [Girle] |
| Full Idea: In possible worlds logics a statement is true-in-a-world rather than just true. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 1.1) | |
| A reaction: This sounds relativist, but I don't think it is. It is the facts which change, not the concept of truth. So 'donkeys can talk' may be true in a world, but not in the actual one. |
| 7788 | Modal logic has four basic modal negation equivalences [Girle] |
| Full Idea: The four important logical equivalences in modal logic (the Modal Negation equivalences) are: ¬◊p↔□¬p, ◊¬p↔¬□p, □p↔¬◊¬p, and ◊p↔¬□¬p. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 1.2) | |
| A reaction: [Possibly is written as a diamond, necessarily a square] These are parallel to a set of equivalences between quantifiers in predicate logic. They are called the four 'modal negation (MN) equivalences'. |
| 7796 | Modal logics were studied in terms of axioms, but now possible worlds semantics is added [Girle] |
| Full Idea: Modal logics were, for a long time, studied in terms of axiom systems. The advent of possible worlds semantics made it possible to study them in a semantic way as well. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 6.5) |
| 7789 | Necessary implication is called 'strict implication'; if successful, it is called 'entailment' [Girle] |
| Full Idea: Necessary implication is often called 'strict implication'. The sort of strict implication found in valid arguments, where the conjunction of the premises necessarily implies the conclusion, is often called 'entailment'. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 1.2) | |
| A reaction: These are basic concept for all logic. |
| 7790 | If an argument is invalid, a truth tree will indicate a counter-example [Girle] |
| Full Idea: The truth trees method for establishing the validity of arguments and formulas is easy to use, and has the advantage that if an argument or formula is not valid, then a counter-example can be retrieved from the tree. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 1.4) |
| 17656 | Being primitive or prior always depends on a constructional system [Goodman] |
| Full Idea: Nothing is primitive or derivationally prior to anything apart from a constructional system. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.4c) | |
| A reaction: Something may be primitive not just because we can't be bothered to analyse it any further, but because even God couldn't analyse it. Maybe. |
| 17661 | We don't recognise patterns - we invent them [Goodman] |
| Full Idea: Recognising patterns is very much a matter of inventing or imposing them. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.7) | |
| A reaction: I take this to be false. |
| 17659 | Reality is largely a matter of habit [Goodman] |
| Full Idea: Reality in a world, like realism in a picture, is largely a matter of habit. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.6) | |
| A reaction: I'm a robust realist, me, but I sort of see what he means. We become steeped in unspoken conventions about how we take our world to be, and filter out anything that conflicts with it. |
| 17657 | We build our world, and ignore anything that won't fit [Goodman] |
| Full Idea: We dismiss as illusory or negligible what cannot be fitted into the architecture of the world we are building. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.4d) | |
| A reaction: I'm trying to think of an example of this, but can't. Maybe poor people are invisible to the rich? |
| 17654 | A world can be full of variety or not, depending on how we sort it [Goodman] |
| Full Idea: A world may be unmanageably heterogeneous or unbearably monotonous according to how events are sorted into kinds. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.4a) | |
| A reaction: We might expect this from the man who invented 'grue', which allows you to classify things that change colour with things that don't. Could you describe a bird as 'might have been a fish', and classify it with fish? ('Projectible'?) |
| 17653 | Things can only be judged the 'same' by citing some respect of sameness [Goodman] |
| Full Idea: Identification rests upon organization into entities and kinds. The response to the question 'Same or not the same?' must always be 'Same what?'. ...Identity or constancy in a world is identity with respect to what is within that world as organised. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.4a) | |
| A reaction: And the gist of his book is that 'organised' is done by us, not by the world. He seems to be committed to the full Geachean relative identity, rather than the mere Wigginsian relative individuation. An unfashionable view! |
| 7800 | Analytic truths are divided into logically and conceptually necessary [Girle] |
| Full Idea: It has been customary to see analytic truths as dividing into the logically necessary and the conceptually necessary. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 7.3) | |
| A reaction: I suspect that this neglected distinction is important in discussions of Quine's elimination of the analytic/synthetic distinction. Was Quine too influenced by what is logically necessary, which might shift with a change of axioms? |
| 7801 | Possibilities can be logical, theoretical, physical, economic or human [Girle] |
| Full Idea: Qualified modalities seem to form a hierarchy, if we say that 'the possibility that there might be no hunger' is possible logically, theoretically, physically, economically, and humanly. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 7.3) | |
| A reaction: Girle also mentions conceptual possibility. I take 'physically' to be the same as 'naturally'. I would take 'metaphysically' possible to equate to 'theoretically' rather than 'logically'. Almost anything might be logically possible, with bizarre logic. |
| 7792 | A world has 'access' to a world it generates, which is important in possible worlds semantics [Girle] |
| Full Idea: When one world generates another then it has 'access' to the world it generated. The accessibility relation between worlds is very important in possible worlds semantics. | |
| From: Rod Girle (Modal Logics and Philosophy [2000], 3.2) | |
| A reaction: This invites the obvious question what is meant by 'generates'. |
| 17660 | Discovery is often just finding a fit, like a jigsaw puzzle [Goodman] |
| Full Idea: Discovery often amounts, as when I place a piece in a jigsaw puzzle, not to arrival at a proposition for declaration or defense, but to finding a fit. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.7) | |
| A reaction: I find Goodman's views here pretty alien, but I like this bit. Coherence really rocks. |
| 17658 | Users of digital thermometers recognise no temperatures in the gaps [Goodman] |
| Full Idea: To use a digital thermometer with readings in tenths of a degree is to recognise no temperature as lying between 90 and 90.1 degrees. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.4d) | |
| A reaction: This appears to be nonsense, treating users of digital thermometers as if they were stupid. No one thinks temperatures go up and down in quantum leaps. We all know there is a gap between instrument and world. (Very American, I'm thinking!) |
| 17650 | We lack frames of reference to transform physics, biology and psychology into one another [Goodman] |
| Full Idea: We have no neat frames of reference, no ready rules for transforming physics, biology and psychology into one another. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.2) |
| 17655 | Grue and green won't be in the same world, as that would block induction entirely [Goodman] |
| Full Idea: Grue cannot be a relevant kind for induction in the same world as green, for that would preclude some of the decisions, right or wrong, that constitute inductive inference. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.4b) | |
| A reaction: This may make 'grue' less mad than I thought it was. I always assume we are slicing the world as 'green, blue and grue'. I still say 'green' is a basic predicate of experience, but 'grue' is amenable to analysis. |
| 17649 | If the world is one it has many aspects, and if there are many worlds they will collect into one [Goodman] |
| Full Idea: If there is but one world, it embraces a multiplicity of contrasting aspects; if there are many worlds, the collection of them all is one. One world may be taken as many, or many worlds taken as one; whether one or many depends on the way of taking. | |
| From: Nelson Goodman (Ways of Worldmaking [1978], 1.2) | |
| A reaction: He cites 'The Pluralistic Universe' by William James for this idea. The idea is that the distinction 'evaporates under analysis'. Parmenides seems to have thought that no features could be distinguished in the true One. |
| 7608 | The world is established, and cannot be moved [Isaiah] |
| Full Idea: The world is also established, that it cannot be moved. | |
| From: Isaiah (23: Book of Isaiah [c.680 BCE], 93.1) | |
| A reaction: This verse caused big trouble for Galileo. The only reason I can think of for Isaiah to write this is that occasionally people were prone to panic, and worry that the Earth might suddenly and abruptly be moved. |
| 7343 | Beside me there is no God [Isaiah] |
| Full Idea: I am the first, and I am the last; and beside me there is no God. | |
| From: Isaiah (23: Book of Isaiah [c.680 BCE], 44.06) | |
| A reaction: This seems to be the first clear statement (c. 680 BCE) of monotheism, certainly preceding any Greek views on the subject (cf. Idea 2629,Idea 7347). It is not just an arrogant assertion by the jews, but a humble sacrifice, donating their god to humanity. |