Ideas from 'Elucidation of some points in E.Schröder' by Gottlob Frege [1895], by Theme Structure

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4. Formal Logic / F. Set Theory ST / 3. Types of Set / b. Empty (Null) Set
A class is an aggregate of objects; if you destroy them, you destroy the class; there is no empty class
                        Full Idea: A class consists of objects; it is an aggregate, a collective unity, of them; if so, it must vanish when these objects vanish. If we burn down all the trees of a wood, we thereby burn down the wood. Thus there can be no empty class.
                        From: Gottlob Frege (Elucidation of some points in E.Schröder [1895], p.212), quoted by Oliver,A/Smiley,T - What are Sets and What are they For?
                        A reaction: This rests on Cantor's view of a set as a collection, rather than on Dedekind, which allows null and singleton sets.