\begin{definition}[Definition:Morse-Kelley Set Theory]
'''Morse-Kelley set theory''' is a system of axiomatic set theory.
It is a stronger form of Zermelo-Fraenkel-Skolem set theory which allows not only for first order formulas to specify the existence of properties of sets, but also defines properties by quantifying over properties as well as over sets.
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{{NamedforDef|Anthony Perry Morse|name2 = John Leroy Kelley|cat = Morse|cat2 = Kelley}}
\end{definition}