# Definition:Naive Set Theory

## Contents

## Definition

**Naïve set theory**, in contrast with axiomatic set theory, is an approach to set theory which assumes the existence of a universal set, despite the fact that such an assumption leads to paradoxes.

A popular alternative (and inaccurate) definition describes this as a

*non-formalized definition of set theory which describes sets and the relations between them using natural language.*

However, the discipline is founded upon quite as rigid a set of axioms, namely, those of propositional and predicate logic.

## Linguistic Note

The pronunciation of **naive** is in two syllables, approximately **nigh- eeve**, and means

**simple**in the sense of

**unsophisticated**. In natural language it is usually used in the sense of

**lacking worldly wisdom**.

The word **naive** should strictly speaking be written **naïve**, with a diaeresis on the **i**. However, $\mathsf{Pr} \infty \mathsf{fWiki}$ follows what appears to be standard practice and renders the word without it.

## Also see

- Results about
**naïve set theory**can be found here.

## Sources

- 1978: Thomas A. Whitelaw:
*An Introduction to Abstract Algebra*... (previous) ... (next): $\S 2$: Introductory remarks on sets: $\text{(g)}$ - 1993: Keith Devlin:
*The Joy of Sets: Fundamentals of Contemporary Set Theory*(2nd ed.) ... (next): $\S 1$: Naive Set Theory - 1996: H. Jerome Keisler and Joel Robbin:
*Mathematical Logic and Computability*... (next): Appendix $\text{A}.1$: Sets - 2000: James R. Munkres:
*Topology*(2nd ed.) ... (next): $1$: Set Theory and Logic