81 ideas
21955 | My dogmatic slumber was first interrupted by David Hume [Kant] |
16931 | Metaphysics is generating a priori knowledge by intuition and concepts, leading to the synthetic [Kant] |
5182 | Claims about 'the Absolute' are not even verifiable in principle [Ayer on Bradley] |
6864 | Metaphysics is finding bad reasons for instinctive beliefs [Bradley] |
13689 | 'Theorems' are formulas provable from no premises at all [Sider] |
13705 | Truth tables assume truth functionality, and are just pictures of truth functions [Sider] |
13710 | In D we add that 'what is necessary is possible'; then tautologies are possible, and contradictions not necessary [Sider] |
13706 | Intuitively, deontic accessibility seems not to be reflexive, but to be serial [Sider] |
13711 | System B introduces iterated modalities [Sider] |
13708 | S5 is the strongest system, since it has the most valid formulas, because it is easy to be S5-valid [Sider] |
13712 | Epistemic accessibility is reflexive, and allows positive and negative introspection (KK and K¬K) [Sider] |
13714 | We can treat modal worlds as different times [Sider] |
13720 | Converse Barcan Formula: □∀αφ→∀α□φ [Sider] |
13718 | The Barcan Formula ∀x□Fx→□∀xFx may be a defect in modal logic [Sider] |
13723 | System B is needed to prove the Barcan Formula [Sider] |
13715 | You can employ intuitionist logic without intuitionism about mathematics [Sider] |
13680 | Maybe logical consequence is a primitive notion [Sider] |
13679 | Maybe logical consequence is more a matter of provability than of truth-preservation [Sider] |
13678 | The most popular account of logical consequence is the semantic or model-theoretic one [Sider] |
13682 | Maybe logical consequence is impossibility of the premises being true and the consequent false [Sider] |
13722 | A 'theorem' is an axiom, or the last line of a legitimate proof [Sider] |
13696 | When a variable is 'free' of the quantifier, the result seems incapable of truth or falsity [Sider] |
13700 | A 'total' function must always produce an output for a given domain [Sider] |
10999 | Names need a means of reidentifying their referents [Bradley, by Read] |
13703 | λ can treat 'is cold and hungry' as a single predicate [Sider] |
13687 | No assumptions in axiomatic proofs, so no conditional proof or reductio [Sider] |
13688 | Good axioms should be indisputable logical truths [Sider] |
13691 | Induction has a 'base case', then an 'inductive hypothesis', and then the 'inductive step' [Sider] |
13690 | Proof by induction 'on the length of the formula' deconstructs a formula into its accepted atoms [Sider] |
13685 | Natural deduction helpfully allows reasoning with assumptions [Sider] |
13686 | We can build proofs just from conclusions, rather than from plain formulae [Sider] |
13697 | Valuations in PC assign truth values to formulas relative to variable assignments [Sider] |
13684 | The semantical notion of a logical truth is validity, being true in all interpretations [Sider] |
13704 | It is hard to say which are the logical truths in modal logic, especially for iterated modal operators [Sider] |
13724 | In model theory, first define truth, then validity as truth in all models, and consequence as truth-preservation [Sider] |
13698 | In a complete logic you can avoid axiomatic proofs, by using models to show consequences [Sider] |
13699 | Compactness surprisingly says that no contradictions can emerge when the set goes infinite [Sider] |
16918 | Mathematics cannot proceed just by the analysis of concepts [Kant] |
16919 | Geometry rests on our intuition of space [Kant] |
16930 | Geometry is not analytic, because a line's being 'straight' is a quality [Kant] |
16920 | Numbers are formed by addition of units in time [Kant] |
16929 | 7+5 = 12 is not analytic, because no analysis of 7+5 will reveal the concept of 12 [Kant] |
13701 | A single second-order sentence validates all of arithmetic - but this can't be proved axiomatically [Sider] |
16910 | Mathematics can only start from an a priori intuition which is not empirical but pure [Kant] |
16917 | All necessary mathematical judgements are based on intuitions of space and time [Kant] |
16928 | Mathematics cannot be empirical because it is necessary, and that has to be a priori [Kant] |
13692 | A 'precisification' of a trivalent interpretation reduces it to a bivalent interpretation [Sider] |
13693 | A 'supervaluation' assigns further Ts and Fs, if they have been assigned in every precisification [Sider] |
13695 | Supervaluational logic is classical, except when it adds the 'Definitely' operator [Sider] |
13694 | We can 'sharpen' vague terms, and then define truth as true-on-all-sharpenings [Sider] |
13683 | A relation is a feature of multiple objects taken together [Sider] |
6422 | Internal relations are said to be intrinsic properties of two terms, and of the whole they compose [Bradley, by Russell] |
7966 | Relations must be linked to their qualities, but that implies an infinite regress of relations [Bradley] |
11833 | The substance, once the predicates are removed, remains unknown to us [Kant] |
13702 | The identity of indiscernibles is necessarily true, if being a member of some set counts as a property [Sider] |
13721 | 'Strong' necessity in all possible worlds; 'weak' necessity in the worlds where the relevant objects exist [Sider] |
13707 | Maybe metaphysical accessibility is intransitive, if a world in which I am a frog is impossible [Sider] |
13709 | Logical truths must be necessary if anything is [Sider] |
13716 | 'If B hadn't shot L someone else would have' if false; 'If B didn't shoot L, someone else did' is true [Sider] |
13717 | Transworld identity is not a problem in de dicto sentences, which needn't identify an individual [Sider] |
13719 | Barcan Formula problem: there might have been a ghost, despite nothing existing which could be a ghost [Sider] |
21957 | 'Transcendental' concerns how we know, rather than what we know [Kant] |
16923 | I admit there are bodies outside us [Kant] |
21441 | 'Transcendental' is not beyond experience, but a prerequisite of experience [Kant] |
6404 | British Idealists said reality is a single Mind which experiences itself [Bradley, by Grayling] |
22299 | Bradley's objective idealism accepts reality (the Absolute), but says we can't fully describe it [Bradley, by Potter] |
21343 | Qualities and relations are mere appearance; the Absolute is a single undifferentiated substance [Bradley, by Heil] |
16916 | A priori synthetic knowledge is only of appearances, not of things in themselves [Kant] |
16915 | A priori intuitions can only concern the objects of our senses [Kant] |
16914 | A priori intuition of objects is only possible by containing the form of my sensibility [Kant] |
21447 | I can make no sense of the red experience being similar to the quality in the object [Kant] |
16924 | I count the primary features of things (as well as the secondary ones) as mere appearances [Kant] |
16913 | I can't intuit a present thing in itself, because the properties can't enter my representations [Kant] |
16925 | Appearance gives truth, as long as it is only used within experience [Kant] |
16911 | Intuition is a representation that depends on the presence of the object [Kant] |
16912 | Some concepts can be made a priori, which are general thoughts of objects, like quantity or cause [Kant] |
16926 | Analytic judgements say clearly what was in the concept of the subject [Kant] |
16927 | Analytic judgement rests on contradiction, since the predicate cannot be denied of the subject [Kant] |
6406 | Reality is one, because plurality implies relations, and they assert a superior unity [Bradley] |
16922 | Space must have three dimensions, because only three lines can meet at right angles [Kant] |
16921 | If all empirical sensation of bodies is removed, space and time are still left [Kant] |