36 ideas
| 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] |
| 17763 | Axiomatic systems are purely syntactic, and do not presuppose any interpretation [Walicki] |
| 17761 | A compact axiomatisation makes it possible to understand a field as a whole [Walicki] |
| 17757 | Members of ordinals are ordinals, and also subsets of ordinals [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] |
| 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] |
| 9240 | Love creates a necessity concerning what to care about [Frankfurt] |
| 468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
| 9228 | Ranking order of desires reveals nothing, because none of them may be considered important [Frankfurt] |
| 9238 | Morality isn't based on reason; moral indignation is quite unlike disapproval of irrationality [Frankfurt] |
| 9232 | It is by caring about things that we infuse the world with importance [Frankfurt] |
| 9234 | If you don't care about at least one thing, you can't find reasons to care about anything [Frankfurt] |
| 9233 | Our criteria for evaluating how to live offer an answer to the problem [Frankfurt] |
| 9229 | What is worthwhile for its own sake alone may be worth very little [Frankfurt] |
| 9235 | Rather than loving things because we value them, I think we value things because we love them [Frankfurt] |
| 9237 | The paradigm case of pure love is not romantic, but that between parents and infants [Frankfurt] |
| 9239 | I value my children for their sake, but I also value my love for them for its own sake [Frankfurt] |
| 9236 | Love can be cool, and it may not involve liking its object [Frankfurt] |
| 9227 | We might not choose a very moral life, if the character or constitution was deficient [Frankfurt] |
| 9230 | People want to fulfill their desires, but also for their desires to be sustained [Frankfurt] |
| 9241 | Loving oneself is not a failing, but is essential to a successful life [Frankfurt] |
| 9300 | Boredom is serious, not just uncomfortable; it threatens our psychic survival [Frankfurt] |
| 9231 | Freedom needs autonomy (rather than causal independence) - embracing our own desires and choices [Frankfurt] |