34 ideas
12585 | Most people can't even define a chair [Peacocke] |
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] |
17742 | Scotus based modality on semantic consistency, instead of on what the future could allow [Walicki] |
12581 | Perceptual concepts causally influence the content of our experiences [Peacocke] |
12579 | Perception has proto-propositions, between immediate experience and concepts [Peacocke] |
12586 | Consciousness of a belief isn't a belief that one has it [Peacocke] |
18568 | Philosophy should merely give necessary and sufficient conditions for concept possession [Peacocke, by Machery] |
18571 | Peacocke's account of possession of a concept depends on one view of counterfactuals [Peacocke, by Machery] |
18572 | Peacocke's account separates psychology from philosophy, and is very sketchy [Machery on Peacocke] |
12577 | Possessing a concept is being able to make judgements which use it [Peacocke] |
12578 | A concept is just what it is to possess that concept [Peacocke] |
12587 | Employing a concept isn't decided by introspection, but by making judgements using it [Peacocke] |
12584 | An analysis of concepts must link them to something unconceptualized [Peacocke] |
9335 | Concepts are constituted by their role in a group of propositions to which we are committed [Peacocke, by Greco] |
9336 | A concept's reference is what makes true the beliefs of its possession conditions [Peacocke, by Horwich] |
1748 | Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius] |
5989 | Archelaus said life began in a primeval slime [Archelaus, by Schofield] |