Ideas from 'What are Sets and What are they For?' by Oliver,A/Smiley,T [2006], by Theme Structure
[found in 'Metaphysics (Philosophical Perspectives 20)' (ed/tr Hawthorne,John) [Blackwell 2006,9781405167925]].
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4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set
14240

The empty set is something, not nothing!

14241

We don't need the empty set to express nonexistence, as there are other ways to do that

14239

The empty set is usually derived from Separation, but it also seems to need Infinity

14242

Maybe we can treat the empty set symbol as just meaning an empty term

4. Formal Logic / F. Set Theory ST / 3. Types of Set / c. Unit (Singleton) Set
14243

The unit set may be needed to express intersections that leave a single member

4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / b. Combinatorial sets
14199

Cantor's sets were just collections, but Dedekind's were containers

5. Theory of Logic / G. Quantification / 6. Plural Quantification
14234

If you only refer to objects one at a time, you need sets in order to refer to a plurality

14237

We can use plural language to refer to the set theory domain, to avoid calling it a 'set'

5. Theory of Logic / I. Semantics of Logic / 3. Logical Truth
14245

Logical truths are true no matter what exists  but predicate calculus insists that something exists

6. Mathematics / A. Nature of Mathematics / 7. Application of Mathematics
14246

If mathematics purely concerned mathematical objects, there would be no applied mathematics

6. Mathematics / B. Foundations for Mathematics / 5. Mathematics as Set Theory / a. Mathematics is set theory
14247

Sets might either represent the numbers, or be the numbers, or replace the numbers
