# Contents

## Idea

A first-order theory is a theory which allows for quantification over variables, but not over sets of variables. It is a theory (= language + axioms) in a language consisting of the language of first-order logic, plus additional relation, function and constant symbols.

The characterization of models over first-order theories is the topic of traditional model theory.

## Examples

Formulation of set theory is a first-order theory, such as

Revised on March 26, 2014 04:40:25 by Urs Schreiber (185.37.147.12)