47 ideas
| 8797 | The negation of all my beliefs about my current headache would be fully coherent [Sosa] |
| 8877 | We can't attain a coherent system by lopping off any beliefs that won't fit [Sosa] |
| 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] |
| 17749 | Post proved the consistency of propositional logic in 1921 [Walicki] |
| 17765 | Propositional language can only relate statements as the same or as different [Walicki] |
| 17764 | Boolean connectives are interpreted as functions on the set {1,0} [Walicki] |
| 17752 | The empty set is useful for defining sets by properties, when the members are not yet known [Walicki] |
| 17753 | The empty set avoids having to take special precautions in case members vanish [Walicki] |
| 17759 | Ordinals play the central role in set theory, providing the model of well-ordering [Walicki] |
| 17741 | To determine the patterns in logic, one must identify its 'building blocks' [Walicki] |
| 13850 | In modern logic all formal validity can be characterised syntactically [Engelbretsen/Sayward] |
| 13849 | Classical logic rests on truth and models, where constructivist logic rests on defence and refutation [Engelbretsen/Sayward] |
| 13851 | Unlike most other signs, = cannot be eliminated [Engelbretsen/Sayward] |
| 17747 | A 'model' of a theory specifies interpreting a language in a domain to make all theorems true [Walicki] |
| 17748 | The L-S Theorem says no theory (even of reals) says more than a natural number theory [Walicki] |
| 17761 | A compact axiomatisation makes it possible to understand a field as a whole [Walicki] |
| 17763 | Axiomatic systems are purely syntactic, and do not presuppose any interpretation [Walicki] |
| 13852 | Axioms are ω-incomplete if the instances are all derivable, but the universal quantification isn't [Engelbretsen/Sayward] |
| 17758 | Ordinals are transitive sets of transitive sets; or transitive sets totally ordered by inclusion [Walicki] |
| 17755 | Ordinals are the empty set, union with the singleton, and any arbitrary union of ordinals [Walicki] |
| 17756 | The union of finite ordinals is the first 'limit ordinal'; 2ω is the second... [Walicki] |
| 17760 | Two infinite ordinals can represent a single infinite cardinal [Walicki] |
| 17757 | Members of ordinals are ordinals, and also subsets of ordinals [Walicki] |
| 17762 | In non-Euclidean geometry, all Euclidean theorems are valid that avoid the fifth postulate [Walicki] |
| 17754 | Inductive proof depends on the choice of the ordering [Walicki] |
| 8884 | The phenomenal concept of an eleven-dot pattern does not include the concept of eleven [Sosa] |
| 8443 | Mereological essentialism says an entity must have exactly those parts [Sosa] |
| 17742 | Scotus based modality on semantic consistency, instead of on what the future could allow [Walicki] |
| 8878 | It is acceptable to say a supermarket door 'knows' someone is approaching [Sosa] |
| 8880 | In reducing arithmetic to self-evident logic, logicism is in sympathy with rationalism [Sosa] |
| 8881 | Most of our knowledge has insufficient sensory support [Sosa] |
| 8794 | There are very few really obvious truths, and not much can be proved from them [Sosa] |
| 8882 | Perception may involve thin indexical concepts, or thicker perceptual concepts [Sosa] |
| 8883 | Do beliefs only become foundationally justified if we fully attend to features of our experience? [Sosa] |
| 8885 | Some features of a thought are known directly, but others must be inferred [Sosa] |
| 8876 | Much propositional knowledge cannot be formulated, as in recognising a face [Sosa] |
| 8796 | A single belief can trail two regresses, one terminating and one not [Sosa] |
| 8799 | If mental states are not propositional, they are logically dumb, and cannot be foundations [Sosa] |
| 8795 | Mental states cannot be foundational if they are not immune to error [Sosa] |
| 8879 | Fully comprehensive beliefs may not be knowledge [Sosa] |
| 8798 | Vision causes and justifies beliefs; but to some extent the cause is the justification [Sosa] |
| 8442 | What law would explain causation in the case of causing a table to come into existence? [Sosa] |
| 8445 | The necessitated is not always a result or consequence of the necessitator [Sosa] |
| 8444 | Where is the necessary causation in the three people being tall making everybody tall? [Sosa] |