Combining Philosophers

All the ideas for Arcesilaus, Brian Clegg and Achille Varzi

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32 ideas

4. Formal Logic / F. Set Theory ST / 2. Mechanics of Set Theory / b. Terminology of ST
A set is 'well-ordered' if every subset has a first element [Clegg]
4. Formal Logic / F. Set Theory ST / 3. Types of Set / d. Infinite Sets
Set theory made a closer study of infinity possible [Clegg]
Any set can always generate a larger set - its powerset, of subsets [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets
Maybe set theory need not be well-founded [Varzi]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / b. Axiom of Extensionality I
Extensionality: Two sets are equal if and only if they have the same elements [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / c. Axiom of Pairing II
Pairing: For any two sets there exists a set to which they both belong [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / d. Axiom of Unions III
Unions: There is a set of all the elements which belong to at least one set in a collection [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / f. Axiom of Infinity V
Infinity: There exists a set of the empty set and the successor of each element [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / g. Axiom of Powers VI
Powers: All the subsets of a given set form their own new powerset [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / j. Axiom of Choice IX
Choice: For every set a mechanism will choose one member of any non-empty subset [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / k. Axiom of Existence
Axiom of Existence: there exists at least one set [Clegg]
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / l. Axiom of Specification
Specification: a condition applied to a set will always produce a new set [Clegg]
4. Formal Logic / G. Formal Mereology / 1. Mereology
Mereology need not be nominalist, though it is often taken to be so [Varzi]
Are there mereological atoms, and are all objects made of them? [Varzi]
There is something of which everything is part, but no null-thing which is part of everything [Varzi]
6. Mathematics / A. Nature of Mathematics / 1. Mathematics
Mathematics can be 'pure' (unapplied), 'real' (physically grounded); or 'applied' (just applicable) [Clegg]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / e. Ordinal numbers
Beyond infinity cardinals and ordinals can come apart [Clegg]
An ordinal number is defined by the set that comes before it [Clegg]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / g. Real numbers
Transcendental numbers can't be fitted to finite equations [Clegg]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / k. Imaginary numbers
By adding an axis of imaginary numbers, we get the useful 'number plane' instead of number line [Clegg]
6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / l. Zero
Either lack of zero made early mathematics geometrical, or the geometrical approach made zero meaningless [Clegg]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / a. The Infinite
Cantor's account of infinities has the shaky foundation of irrational numbers [Clegg]
6. Mathematics / A. Nature of Mathematics / 5. The Infinite / g. Continuum Hypothesis
The Continuum Hypothesis is independent of the axioms of set theory [Clegg]
The 'continuum hypothesis' says aleph-one is the cardinality of the reals [Clegg]
9. Objects / C. Structure of Objects / 5. Composition of an Object
'Composition is identity' says multitudes are the reality, loosely composing single things [Varzi]
9. Objects / C. Structure of Objects / 8. Parts of Objects / a. Parts of objects
Parts may or may not be attached, demarcated, arbitrary, material, extended, spatial or temporal [Varzi]
If 'part' is reflexive, then identity is a limit case of parthood [Varzi]
'Part' stands for a reflexive, antisymmetric and transitive relation [Varzi]
The parthood relation will help to define at least seven basic predicates [Varzi]
9. Objects / C. Structure of Objects / 8. Parts of Objects / c. Wholes from parts
Sameness of parts won't guarantee identity if their arrangement matters [Varzi]
10. Modality / D. Knowledge of Modality / 4. Conceivable as Possible / b. Conceivable but impossible
Conceivability may indicate possibility, but literary fantasy does not [Varzi]
13. Knowledge Criteria / D. Scepticism / 3. Illusion Scepticism
A false object might give the same presentation as a true one [Arcesilaus, by Cicero]