18 ideas
13913 | The four 'perfect syllogisms' are called Barbara, Celarent, Darii and Ferio [Engelbretsen/Sayward] |
13914 | Syllogistic logic has one rule: what is affirmed/denied of wholes is affirmed/denied of their parts [Engelbretsen/Sayward] |
13915 | Syllogistic can't handle sentences with singular terms, or relational terms, or compound sentences [Engelbretsen/Sayward] |
13916 | Term logic uses expression letters and brackets, and '-' for negative terms, and '+' for compound terms [Engelbretsen/Sayward] |
13010 | In order to select the logic justified by experience, we would need to use a lot of logic [Boghossian on Quine] |
13850 | In modern logic all formal validity can be characterised syntactically [Engelbretsen/Sayward] |
9002 | Elementary logic requires truth-functions, quantifiers (and variables), identity, and also sets of variables [Quine] |
13849 | Classical logic rests on truth and models, where constructivist logic rests on defence and refutation [Engelbretsen/Sayward] |
13681 | Logical consequence is marked by being preserved under all nonlogical substitutions [Quine, by Sider] |
13851 | Unlike most other signs, = cannot be eliminated [Engelbretsen/Sayward] |
13829 | If logical truths essentially depend on logical constants, we had better define the latter [Hacking on Quine] |
13852 | Axioms are ω-incomplete if the instances are all derivable, but the universal quantification isn't [Engelbretsen/Sayward] |
9003 | Set theory was struggling with higher infinities, when new paradoxes made it baffling [Quine] |
9004 | If set theory is not actually a branch of logic, then Frege's derivation of arithmetic would not be from logic [Quine] |
9006 | Commitment to universals is as arbitrary or pragmatic as the adoption of a new system of bookkeeping [Quine] |
9001 | Frege moved Kant's question about a priori synthetic to 'how is logical certainty possible?' [Quine] |
9005 | Examination of convention in the a priori begins to blur the distinction with empirical knowledge [Quine] |
12709 | Motion is not absolute, but consists in relation [Leibniz] |