In
mathematical logic,
New Foundations (
NF) is an
axiomatic set theory, conceived by
Willard Van Orman Quine as a simplification of the
theory of types of
Principia Mathematica. Quine first proposed NF in a 1937 article titled "New Foundations for Mathematical Logic"; hence the name. Much of this entry discusses
NFU, an important variant of NF due to Jensen (1969) and exposited in Holmes (1998). In 1940 and 1951 Quine introduced an extension of NF sometimes called "Mathematical Logic" or "ML", that included classes as well as sets.