95 ideas
15186 | In the tenseless view, all times are equally real, so statements of the future have truth-values [Le Poidevin] |
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] |
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] |
13727 | A 'constant' domain is the same for all worlds; 'varying' domains can be entirely separate [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] |
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] |
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] |
13143 | Universal: a) if σ ¬◊X then σ.m ¬X b) if σ □X then σ.m X [m exists] [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] |
13141 | Negation: if σ ¬¬X then σ X [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] |
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] |
13144 | T reflexive: a) if σ □X then σ X b) if σ ¬◊X then σ ¬X [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] |
13147 | 4 transitive: a) if σ □X then σ.n □X b) if σ ¬◊X then σ.n ¬◊X [n occurs] [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] |
13145 | D serial: a) if σ □X then σ ◊X b) if σ ¬◊X then σ ¬□X [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] |
13111 | Read epistemic box as 'a knows/believes P' and diamond as 'for all a knows/believes, P' [Fitting/Mendelsohn] |
13112 | In epistemic logic knowers are logically omniscient, so they know that they know [Fitting/Mendelsohn] |
13113 | F: will sometime, P: was sometime, G: will always, H: was always [Fitting/Mendelsohn] |
13729 | The Barcan corresponds to anti-monotonicity, and the Converse to monotonicity [Fitting/Mendelsohn] |
13728 | The Barcan says nothing comes into existence; the Converse says nothing ceases; the pair imply stability [Fitting/Mendelsohn] |
9725 | 'Predicate abstraction' abstracts predicates from formulae, giving scope for constants and functions [Fitting/Mendelsohn] |
22919 | A thing which makes no difference seems unlikely to exist [Le Poidevin] |
18528 | The single imagined 'interval' between things only exists in the intellect [Auriol] |
13730 | The Indiscernibility of Identicals has been a big problem for modal logic [Fitting/Mendelsohn] |
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] |
15207 | We want illuminating theories, rather than coherent theories [Le Poidevin] |
22926 | In addition to causal explanations, they can also be inferential, or definitional, or purposive [Le Poidevin] |
22932 | We don't just describe a time as 'now' from a private viewpoint, but as a fact about the world [Le Poidevin] |
6866 | It is disturbing if we become unreal when we die, but if time is unreal, then we remain real after death [Le Poidevin] |
15190 | Evil can't be an illusion, because then the illusion that there is evil would be evil [Le Poidevin] |
6867 | Existentialism focuses on freedom and self-making, and insertion into the world [Le Poidevin] |
16589 | Prime matter lacks essence, but is only potentially and indeterminately a physical thing [Auriol] |
22927 | The logical properties of causation are asymmetry, transitivity and irreflexivity [Le Poidevin] |
22922 | We can identify unoccupied points in space, so they must exist [Le Poidevin] |
22924 | If spatial points exist, then they must be stationary, by definition [Le Poidevin] |
22923 | Absolute space explains actual and potential positions, and geometrical truths [Le Poidevin] |
22928 | For relationists moving an object beyond the edge of space creates new space [Le Poidevin] |
22931 | We distinguish time from space, because it passes, and it has a unique present moment [Le Poidevin] |
22917 | Since nothing occurs in a temporal vacuum, there is no way to measure its length [Le Poidevin] |
22921 | Temporal vacuums would be unexperienced, unmeasured, and unending [Le Poidevin] |
15195 | If the future is not real, we don't seem to have any obligation to future individuals [Le Poidevin] |
15188 | If things don't persist through time, then change makes no sense [Le Poidevin] |
22934 | Time can't speed up or slow down, so it doesn't seem to be a 'process' [Le Poidevin] |
15191 | At the very least, minds themselves seem to be tensed [Le Poidevin] |
15197 | Fiction seems to lack a tensed perspective, and offers an example of tenseless language [Le Poidevin] |
15206 | It is the view of the future that really decides between tensed and tenseless views of time [Le Poidevin] |
15198 | In the B-series, time-positions are unchanging; in the A-series they change (from future to present to past) [Le Poidevin] |
15189 | Things which have ceased change their A-series position; things that persist change their B-series position [Le Poidevin] |
6865 | A-theory says past, present, future and flow exist; B-theory says this just reports our perspective [Le Poidevin] |
15187 | It is claimed that the tense view entails the unreality of both future and past [Le Poidevin] |
15205 | Tensed theorists typically try to reduce the tenseless to the tensed [Le Poidevin] |
15192 | We share a common now, but not a common here [Le Poidevin] |
15193 | The new tenseless theory offers indexical truth-conditions, instead of a reductive analysis [Le Poidevin] |
22938 | To say that the past causes the present needs them both to be equally real [Le Poidevin] |
22939 | The B-series doesn't seem to allow change [Le Poidevin] |
22940 | If the B-universe is eternal, why am I trapped in a changing moment of it? [Le Poidevin] |
22947 | An ordered series can be undirected, but time favours moving from earlier to later [Le Poidevin] |
22952 | If time's arrow is causal, how can there be non-simultaneous events that are causally unconnected? [Le Poidevin] |
22953 | Time's arrow is not causal if there is no temporal gap between cause and effect [Le Poidevin] |
22951 | If time's arrow is psychological then different minds can impose different orders on events [Le Poidevin] |
22948 | There are Thermodynamic, Psychological and Causal arrows of time [Le Poidevin] |
22949 | Presumably if time's arrow is thermodynamic then time ends when entropy is complete [Le Poidevin] |
22950 | If time is thermodynamic then entropy is necessary - but the theory says it is probable [Le Poidevin] |
22943 | Instantaneous motion is an intrinsic disposition to be elsewhere [Le Poidevin] |
22945 | The dynamic view of motion says it is primitive, and not reducible to objects, properties and times [Le Poidevin] |
22937 | If the present could have diverse pasts, then past truths can't have present truthmakers [Le Poidevin] |
22925 | The present is the past/future boundary, so the first moment of time was not present [Le Poidevin] |
22944 | The primitive parts of time are intervals, not instants [Le Poidevin] |
22942 | If time is infinitely divisible, then the present must be infinitely short [Le Poidevin] |
22946 | The multiverse is distinct time-series, as well as spaces [Le Poidevin] |
16651 | God can do anything non-contradictory, as making straightness with no line, or lightness with no parts [Auriol] |
15196 | God being inside or outside of time both raise a group of difficult problems [Le Poidevin] |
22941 | How could a timeless God know what time it is? So could God be both timeless and omniscient? [Le Poidevin] |