75 ideas
12780 | We can grasp the wisdom of God a priori [Leibniz] |
17729 | Examining concepts can recover information obtained through the senses [Jenkins] |
17740 | Instead of correspondence of proposition to fact, look at correspondence of its parts [Jenkins] |
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] |
13706 | Intuitively, deontic accessibility seems not to be reflexive, but to be serial [Sider] |
13710 | In D we add that 'what is necessary is possible'; then tautologies are possible, and contradictions not necessary [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] |
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] |
13680 | Maybe logical consequence is a primitive notion [Sider] |
13679 | Maybe logical consequence is more a matter of provability than of truth-preservation [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] |
13703 | λ can treat 'is cold and hungry' as a single predicate [Sider] |
13688 | Good axioms should be indisputable logical truths [Sider] |
13687 | No assumptions in axiomatic proofs, so no conditional proof or reductio [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] |
17730 | Combining the concepts of negation and finiteness gives the concept of infinity [Jenkins] |
13701 | A single second-order sentence validates all of arithmetic - but this can't be proved axiomatically [Sider] |
17719 | Arithmetic concepts are indispensable because they accurately map the world [Jenkins] |
17717 | Senses produce concepts that map the world, and arithmetic is known through these concepts [Jenkins] |
17724 | It is not easy to show that Hume's Principle is analytic or definitive in the required sense [Jenkins] |
17727 | We can learn about the world by studying the grounding of our concepts [Jenkins] |
17720 | There's essential, modal, explanatory, conceptual, metaphysical and constitutive dependence [Jenkins, by PG] |
12774 | Without a substantial chain to link monads, they would just be coordinated dreams [Leibniz] |
12777 | Monads do not make a unity unless a substantial chain is added to them [Leibniz] |
12782 | Monads control nothing outside of themselves [Leibniz] |
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] |
17728 | The concepts we have to use for categorising are ones which map the real world well [Jenkins] |
13683 | A relation is a feature of multiple objects taken together [Sider] |
12778 | There is active and passive power in the substantial chain and in the essence of a composite [Leibniz] |
12783 | Primitive force is what gives a composite its reality [Leibniz] |
12775 | Things seem to be unified if we see duration, position, interaction and connection [Leibniz] |
12776 | Every substance is alive [Leibniz] |
12753 | A substantial bond of powers is needed to unite composites, in addition to monads [Leibniz] |
12781 | A composite substance is a mere aggregate if its essence is just its parts [Leibniz] |
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] |
12779 | There is a reason why not every possible thing exists [Leibniz] |
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] |
17726 | Examining accurate, justified or grounded concepts brings understanding of the world [Jenkins] |
17734 | It is not enough that intuition be reliable - we need to know why it is reliable [Jenkins] |
17723 | Knowledge is true belief which can be explained just by citing the proposition believed [Jenkins] |
12785 | Truth is mutually agreed perception [Leibniz] |
17718 | Grounded concepts are trustworthy maps of the world [Jenkins] |
17739 | The physical effect of world on brain explains the concepts we possess [Jenkins] |
17731 | Verificationism is better if it says meaningfulness needs concepts grounded in the senses [Jenkins] |
17732 | Success semantics explains representation in terms of success in action [Jenkins] |
17725 | 'Analytic' can be conceptual, or by meaning, or predicate inclusion, or definition... [Jenkins] |
12784 | Allow no more miracles than are necessary [Leibniz] |