Classes

Overview

The Zermelo-Fraenkel alternative avoids speaking of collections defined using set theoretical notation that are not sets. The von Neumann-Bernays alternative calls these classes.

Function-Class

A function-class $H$ is a class of ordered pairs that satisfies the definition of being a function except that it may not be a set. That is, for all $⟨x,y_1⟩\in H$, if $⟨x,y_2⟩\in H$, then it follows that $y_1=y_2$.