---
tag: H3V6N71ZYD
kind: concept
name: Double extension set theory
sources:
  - wikipedia: en:68403860@r1041093450
    locator: Double extension set theory
    note: adopted
    mention: wikipedia://en/68403860
    sections: [Summary]
same_as:
  wikidata: Q108146676
  wikipedia: Double extension set theory
inventory: [M210YHVYSX]
---

## Summary

In mathematics, the **Double extension set theory (DEST)** is an axiomatic set theory proposed by Andrzej Kisielewicz consisting of two separate membership relations on the universe of sets, denoted here by $\in$ and $\varepsilon$, and a set of axioms relating the two. The intention behind defining the two membership relations is to avoid the usual paradoxes of set theory, without substantially weakening the axiom of unrestricted comprehension.