Combining Texts

All the ideas for 'That Politics may be reduced to a Science', 'works' and 'Elements of Set Theory'

expand these ideas     |    start again     |     specify just one area for these texts

13 ideas

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
7791 The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle]
4. Formal Logic / F. Set Theory ST / 2. Mechanics of Set Theory / b. Terminology of ST
13201 ∈ says the whole set is in the other; ⊆ says the members of the subset are in the other [Enderton]
13204 The 'ordered pair' <x,y> is defined to be {{x}, {x,y}} [Enderton]
13206 A 'linear or total ordering' must be transitive and satisfy trichotomy [Enderton]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set
13200 Note that {Φ} =/= Φ, because Φ ∈ {Φ} but Φ ∉ Φ [Enderton]
13199 The empty set may look pointless, but many sets can be constructed from it [Enderton]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / c. Unit (Singleton) Sets
13203 The singleton is defined using the pairing axiom (as {x,x}) [Enderton]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / h. Axiom of Replacement VII
13202 Fraenkel added Replacement, to give a theory of ordinal numbers [Enderton]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
13205 We can only define functions if Choice tells us which items are involved [Enderton]
10. Modality / A. Necessity / 2. Nature of Necessity
11002 Equating necessity with informal provability is the S4 conception of necessity [Lewis,CI, by Read]
23. Ethics / C. Virtue Theory / 4. External Goods / d. Friendship
21093 Friendship without community spirit misses out on the main part of virtue [Hume]
24. Political Theory / B. Nature of a State / 3. Constitutions
21091 It would be absurd if even a free constitution did not impose restraints, for the public good [Hume]
24. Political Theory / C. Ruling a State / 2. Leaders / d. Elites
21092 Nobility either share in the power of the whole, or they compose the power of the whole [Hume]