more from Michael Hallett

### Single Idea 17837

#### [catalogued under 4. Formal Logic / F. Set Theory ST / 7. Natural Sets]

Full Idea

Unlike earlier writers (such as Fraenkel), Zermelo clearly allows that there might be ur-elements (that is, objects other than the empty set, which have no members). Indeed he sees in this the possibility of widespread application of set-theory.

Gist of Idea

Zermelo allows ur-elements, to enable the widespread application of set-theory

Source

Michael Hallett (Introduction to Zermelo's 1930 paper [1996], p.1217)

Book Reference

'From Kant to Hilbert: sourcebook Vol. 2', ed/tr. Ewald,William [OUP 1996], p.1217