Combining Texts

All the ideas for 'Causation in a Physical World', 'Remarks on the forces of inorganic Nature' and 'Elements of Set Theory'

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13 ideas

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]
26. Natural Theory / C. Causation / 1. Causation
Explain single events by general rules, or vice versa, or probability explains both, or they are unconnected [Field,H]
26. Natural Theory / C. Causation / 5. Direction of causation
Physical laws are largely time-symmetric, so they make a poor basis for directional causation [Field,H]
Identifying cause and effect is not just conventional; we explain later events by earlier ones [Field,H]
The only reason for adding the notion of 'cause' to fundamental physics is directionality [Field,H]
27. Natural Reality / A. Classical Physics / 1. Mechanics / d. Gravity
Gravity isn't a force, because it produces effects without diminishing [Mayer]