Often synonymous to anti-foundationalism, non-essentialism in philosophy is the non-belief in an essence (from Latin esse) of any given thing, idea, or metaphysical entity (e.g. God). Non-essentialism might also be defined cataphatically (i.e. affirmatively; see cataphatic theology) as the belief that for any entity, there are no specific traits or ground of being which entities of that kind must possess to be considered "that entity".
Non-essentialism is not restricted to general philosophical speculation. It is also found in academic disciplines such as sociology, anthropology, theology, history/historiography and science. How non-essentialism is used in these discourses varies a bit given their different content and subject matter.
Edward Feser describes the position as not only untenable logically but psychologically impossible. In his book Aristotle's Revenge he argues that one cannot say the universe essentially does not have an essence without violating the Law of noncontradiction.[1]