Combining Texts

All the ideas for 'On Duties ('De Officiis')', 'The Secret Connexion' and 'Elements of Set Theory'

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12 ideas

1. Philosophy / A. Wisdom / 1. Nature of Wisdom
Cicero sees wisdom in terms of knowledge, but earlier Stoics saw it as moral [Cicero, by Long]
1. Philosophy / A. Wisdom / 2. Wise People
Unfortunately we choose a way of life before we are old enough to think clearly [Cicero]
4. Formal Logic / F. Set Theory ST / 2. Mechanics of Set Theory / b. Terminology of ST
∈ says the whole set is in the other; ⊆ says the members of the subset are in the other [Enderton]
The 'ordered pair' <x,y> is defined to be {{x}, {x,y}} [Enderton]
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
Note that {Φ} =/= Φ, because Φ ∈ {Φ} but Φ ∉ Φ [Enderton]
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
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
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
We can only define functions if Choice tells us which items are involved [Enderton]
23. Ethics / D. Deontological Ethics / 3. Universalisability
The essence of propriety is consistency [Cicero]
26. Natural Theory / C. Causation / 9. General Causation / a. Constant conjunction
A phenomenalist about objects has to be a regularity theorist about causation [Strawson,G]