New Foundations
axiomatic set theory permitting set comprehension by stratified formulae, hence with a universal set, but in which the singleton map 𝑥↦{𝑥} fails to exist
en-US/ˈnu faʊnˈdeɪʃənz/
en-GB/ˈnjuː faʊnˈdeɪʃənz/
axiomatic set theory permitting set comprehension by stratified formulae, hence with a universal set, but in which the singleton map 𝑥↦{𝑥} fails to exist