22 ideas
10911 | Part-whole is the key relation among truth-makers [Mulligan/Simons/Smith] |
Full Idea: The most important (ontological) relations holding among truth-makers are the part and whole relations. | |
From: Mulligan/Simons/Smith (Truth-makers [1984], §6) | |
A reaction: Hence Peter Simons goes off and writes the best known book on mereology. Looks very promising to me. |
10909 | Truth-makers cannot be the designata of the sentences they make true [Mulligan/Simons/Smith] |
Full Idea: Truth-makers cannot be the designata of the sentences they make true, because sentences with more than one truth-maker would then be ambiguous, and 'a' and 'a exists' would have the same designatum. | |
From: Mulligan/Simons/Smith (Truth-makers [1984], §3) |
10906 | Moments (objects which cannot exist alone) may serve as truth-makers [Mulligan/Simons/Smith] |
Full Idea: A 'moment' is an existentially dependent or non-self-sufficient object, that is, an object which is of such a nature that it cannot exist alone, ....... and we suggest that moments could serve as truth-makers. | |
From: Mulligan/Simons/Smith (Truth-makers [1984], §2) | |
A reaction: [These three writers invented the term 'truth-maker'] |
10907 | The truth-maker for a sentence may not be unique, or may be a combination, or several separate items [Mulligan/Simons/Smith] |
Full Idea: A proposition may have a minimal truth-maker which is not unique, or a sentence may be made true by no single truth-maker but only by several jointly, or again only by several separately. | |
From: Mulligan/Simons/Smith (Truth-makers [1984], §3) |
10912 | Despite negative propositions, truthmakers are not logical complexes, but ordinary experiences [Mulligan/Simons/Smith] |
Full Idea: Because of negative propositions, investigators of truth-makers have said that they are special non-objectual entities with a logical complexity, but we think a theory is possible in which the truth relation is tied to ordinary and scientific experience. | |
From: Mulligan/Simons/Smith (Truth-makers [1984], §6) |
10908 | Correspondence has to invoke facts or states of affairs, just to serve as truth-makers [Mulligan/Simons/Smith] |
Full Idea: The correspondence theory of truth invokes a special category of non-objectual entities - facts, states of affairs, or whatever - simply to serve as truth-makers. | |
From: Mulligan/Simons/Smith (Truth-makers [1984], §3) |
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) |
13007 | Archimedes defined a straight line as the shortest distance between two points [Archimedes, by Leibniz] |
Full Idea: Archimedes gave a sort of definition of 'straight line' when he said it is the shortest line between two points. | |
From: report of Archimedes (fragments/reports [c.240 BCE]) by Gottfried Leibniz - New Essays on Human Understanding 4.13 | |
A reaction: Commentators observe that this reduces the purity of the original Euclidean axioms, because it involves distance and measurement, which are absent from the purest geometry. |
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'. |