85 ideas
21959 | Metaphysics is the most general attempt to make sense of things [Moore,AW] |
11832 | We learn a concept's relations by using it, without reducing it to anything [Wiggins] |
9738 | Each line of a truth table is a model [Fitting/Mendelsohn] |
9727 | Modal logic adds □ (necessarily) and ◊ (possibly) to classical logic [Fitting/Mendelsohn] |
9726 | We let 'R' be the accessibility relation: xRy is read 'y is accessible from x' [Fitting/Mendelsohn] |
9737 | The symbol ||- is the 'forcing' relation; 'Γ ||- P' means that P is true in world Γ [Fitting/Mendelsohn] |
13136 | The prefix σ names a possible world, and σ.n names a world accessible from that one [Fitting/Mendelsohn] |
13727 | A 'constant' domain is the same for all worlds; 'varying' domains can be entirely separate [Fitting/Mendelsohn] |
9734 | Modern modal logic introduces 'accessibility', saying xRy means 'y is accessible from x' [Fitting/Mendelsohn] |
9736 | A 'model' is a frame plus specification of propositions true at worlds, written < G,R,||- > [Fitting/Mendelsohn] |
9735 | A 'frame' is a set G of possible worlds, with an accessibility relation R, written < G,R > [Fitting/Mendelsohn] |
9741 | Accessibility relations can be 'reflexive' (self-referring), 'transitive' (carries over), or 'symmetric' (mutual) [Fitting/Mendelsohn] |
13141 | Negation: if σ ¬¬X then σ X [Fitting/Mendelsohn] |
13138 | Disj: a) if σ ¬(X∨Y) then σ ¬X and σ ¬Y b) if σ X∨Y then σ X or σ Y [Fitting/Mendelsohn] |
13142 | Existential: a) if σ ◊X then σ.n X b) if σ ¬□X then σ.n ¬X [n is new] [Fitting/Mendelsohn] |
13144 | T reflexive: a) if σ □X then σ X b) if σ ¬◊X then σ ¬X [Fitting/Mendelsohn] |
13145 | D serial: a) if σ □X then σ ◊X b) if σ ¬◊X then σ ¬□X [Fitting/Mendelsohn] |
13146 | B symmetric: a) if σ.n □X then σ X b) if σ.n ¬◊X then σ ¬X [n occurs] [Fitting/Mendelsohn] |
13147 | 4 transitive: a) if σ □X then σ.n □X b) if σ ¬◊X then σ.n ¬◊X [n occurs] [Fitting/Mendelsohn] |
13148 | 4r rev-trans: a) if σ.n □X then σ □X b) if σ.n ¬◊X then σ ¬◊X [n occurs] [Fitting/Mendelsohn] |
9740 | If a proposition is possibly true in a world, it is true in some world accessible from that world [Fitting/Mendelsohn] |
9739 | If a proposition is necessarily true in a world, it is true in all worlds accessible from that world [Fitting/Mendelsohn] |
13137 | Conj: a) if σ X∧Y then σ X and σ Y b) if σ ¬(X∧Y) then σ ¬X or σ ¬Y [Fitting/Mendelsohn] |
13140 | Bicon: a)if σ(X↔Y) then σ(X→Y) and σ(Y→X) b) [not biconditional, one or other fails] [Fitting/Mendelsohn] |
13139 | Implic: a) if σ ¬(X→Y) then σ X and σ ¬Y b) if σ X→Y then σ ¬X or σ Y [Fitting/Mendelsohn] |
13143 | Universal: a) if σ ¬◊X then σ.m ¬X b) if σ □X then σ.m X [m exists] [Fitting/Mendelsohn] |
13149 | S5: a) if n ◊X then kX b) if n ¬□X then k ¬X c) if n □X then k X d) if n ¬◊X then k ¬X [Fitting/Mendelsohn] |
9742 | The system K has no accessibility conditions [Fitting/Mendelsohn] |
13114 | □P → P is not valid in D (Deontic Logic), since an obligatory action may be not performed [Fitting/Mendelsohn] |
9743 | The system D has the 'serial' conditon imposed on its accessibility relation [Fitting/Mendelsohn] |
9744 | The system T has the 'reflexive' conditon imposed on its accessibility relation [Fitting/Mendelsohn] |
9746 | The system K4 has the 'transitive' condition on its accessibility relation [Fitting/Mendelsohn] |
9745 | The system B has the 'reflexive' and 'symmetric' conditions on its accessibility relation [Fitting/Mendelsohn] |
9747 | The system S4 has the 'reflexive' and 'transitive' conditions on its accessibility relation [Fitting/Mendelsohn] |
9748 | System S5 has the 'reflexive', 'symmetric' and 'transitive' conditions on its accessibility relation [Fitting/Mendelsohn] |
9404 | Modality affects content, because P→◊P is valid, but ◊P→P isn't [Fitting/Mendelsohn] |
13112 | In epistemic logic knowers are logically omniscient, so they know that they know [Fitting/Mendelsohn] |
13111 | Read epistemic box as 'a knows/believes P' and diamond as 'for all a knows/believes, P' [Fitting/Mendelsohn] |
13113 | F: will sometime, P: was sometime, G: will always, H: was always [Fitting/Mendelsohn] |
13728 | The Barcan says nothing comes into existence; the Converse says nothing ceases; the pair imply stability [Fitting/Mendelsohn] |
13729 | The Barcan corresponds to anti-monotonicity, and the Converse to monotonicity [Fitting/Mendelsohn] |
11863 | (λx)[Man x] means 'the property x has iff x is a man'. [Wiggins] |
9725 | 'Predicate abstraction' abstracts predicates from formulae, giving scope for constants and functions [Fitting/Mendelsohn] |
14746 | What exists can't depend on our conceptual scheme, and using all conceptual schemes is too liberal [Sider on Wiggins] |
11900 | We can accept criteria of distinctness and persistence, without making the counterfactual claims [Mackie,P on Wiggins] |
11870 | Activity individuates natural things, functions do artefacts, and intentions do artworks [Wiggins] |
11866 | The idea of 'thisness' is better expressed with designation/predication and particular/universal [Wiggins] |
11896 | A sortal essence is a thing's principle of individuation [Wiggins, by Mackie,P] |
15835 | Wiggins's sortal essentialism rests on a thing's principle of individuation [Wiggins, by Mackie,P] |
11841 | The evening star is the same planet but not the same star as the morning star, since it is not a star [Wiggins] |
10679 | 'Sortalism' says parts only compose a whole if it falls under a sort or kind [Wiggins, by Hossack] |
14363 | Identity a=b is only possible with some concept to give persistence and existence conditions [Wiggins, by Strawson,P] |
14364 | A thing is necessarily its highest sortal kind, which entails an essential constitution [Wiggins, by Strawson,P] |
11851 | Many predicates are purely generic, or pure determiners, rather than sortals [Wiggins] |
11865 | The possibility of a property needs an essential sortal concept to conceive it [Wiggins] |
14744 | Objects can only coincide if they are of different kinds; trees can't coincide with other trees [Wiggins, by Sider] |
11852 | Is the Pope's crown one crown, if it is made of many crowns? [Wiggins] |
11875 | Boundaries are not crucial to mountains, so they are determinate without a determinate extent [Wiggins] |
14749 | Identity is an atemporal relation, but composition is relative to times [Wiggins, by Sider] |
11844 | If I destroy an item, I do not destroy each part of it [Wiggins] |
11861 | We can forget about individual or particularized essences [Wiggins] |
11871 | Essences are not explanations, but individuations [Wiggins] |
11879 | Essentialism is best represented as a predicate-modifier: □(a exists → a is F) [Wiggins, by Mackie,P] |
11835 | The nominal essence is the idea behind a name used for sorting [Wiggins] |
11876 | It is easier to go from horses to horse-stages than from horse-stages to horses [Wiggins] |
11858 | The question is not what gets the title 'Theseus' Ship', but what is identical with the original [Wiggins] |
11843 | Identity over a time and at a time aren't different concepts [Wiggins] |
11864 | Hesperus=Hesperus, and Phosphorus=Hesperus, so necessarily Phosphorus=Hesperus [Wiggins] |
11831 | The formal properties of identity are reflexivity and Leibniz's Law [Wiggins] |
14362 | Relative Identity is incompatible with the Indiscernibility of Identicals [Wiggins, by Strawson,P] |
11838 | Relativity of Identity makes identity entirely depend on a category [Wiggins] |
11847 | To identify two items, we must have a common sort for them [Wiggins] |
13730 | The Indiscernibility of Identicals has been a big problem for modal logic [Fitting/Mendelsohn] |
11839 | Do both 'same f as' and '=' support Leibniz's Law? [Wiggins] |
11845 | Substitutivity, and hence most reasoning, needs Leibniz's Law [Wiggins] |
11869 | Possible worlds rest on the objects about which we have suppositions [Wiggins] |
11850 | Not every story corresponds to a possible world [Wiggins] |
13725 | □ must be sensitive as to whether it picks out an object by essential or by contingent properties [Fitting/Mendelsohn] |
13731 | Objects retain their possible properties across worlds, so a bundle theory of them seems best [Fitting/Mendelsohn] |
13726 | Counterpart relations are neither symmetric nor transitive, so there is no logic of equality for them [Fitting/Mendelsohn] |
21958 | Appearances are nothing beyond representations, which is transcendental ideality [Moore,AW] |
11848 | Asking 'what is it?' nicely points us to the persistence of a continuing entity [Wiggins] |
11859 | The mind conceptualizes objects; yet objects impinge upon the mind [Wiggins] |
11836 | We can use 'concept' for the reference, and 'conception' for sense [Wiggins] |
11860 | Lawlike propensities are enough to individuate natural kinds [Wiggins] |