38 ideas
| 3123 | Science is in the business of carving nature at the joints [Segal] |
| 3125 | Psychology studies the way rationality links desires and beliefs to causality [Segal] |
| 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] |
| 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] |
| 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] |
| 12887 | A whole must have one characteristic, an internal relation, and a structure [Rescher/Oppenheim] |
| 17742 | Scotus based modality on semantic consistency, instead of on what the future could allow [Walicki] |
| 3105 | Is 'Hesperus = Phosphorus' metaphysically necessary, but not logically or epistemologically necessary? [Segal] |
| 3106 | If claims of metaphysical necessity are based on conceivability, we should be cautious [Segal] |
| 3113 | The success and virtue of an explanation do not guarantee its truth [Segal] |
| 3112 | Folk psychology is ridiculously dualist in its assumptions [Segal] |
| 3108 | If 'water' has narrow content, it refers to both H2O and XYZ [Segal] |
| 3110 | Humans are made of H2O, so 'twins' aren't actually feasible [Segal] |
| 3124 | Externalists can't assume old words refer to modern natural kinds [Segal] |
| 3117 | Concepts can survive a big change in extension [Segal] |
| 3104 | Must we relate to some diamonds to understand them? [Segal] |
| 3103 | Maybe content involves relations to a language community [Segal] |
| 3111 | Externalism can't explain concepts that have no reference [Segal] |
| 3109 | If content is external, so are beliefs and desires [Segal] |
| 3116 | Maybe experts fix content, not ordinary users [Segal] |
| 3121 | If content is narrow, my perfect twin shares my concepts [Segal] |
| 3118 | If thoughts ARE causal, we can't explain how they cause things [Segal] |
| 3119 | Even 'mass' cannot be defined in causal terms [Segal] |