The Reconstructionist Movement is a twentieth-century reaction from within the Conservative movement. It generally accepts the conclusions of philosopher Mordechai Kaplan as its axioms. It rejects the concept of a deity, and regards Judaism as ‘an evolving civilization’; whereas Reform regards Judaism as ‘a religion’ in the Western sense, and whereas Orthodox communities and the Conservative Movement see Judaism as ‘a people’ who happen to be bound by a specific covenant with God.
These philosophies differ over how a mitzvah becomes a mitzvah, and conversely what makes any behavior a transgression. Reform theology regards each individual Jew as the sole arbiter of what Jewish tradition demands of them. Orthodox and Conservative theologies regard the community’s rabbi as the authority. Reconstructionism regards the local Jewish community as the arbiter of what is (or is not) a mitzvah. But Reconstructionism does require the community to reach certain conclusions. For example, identical roles for men and women is a fundamental tenet of Reconstructionism. It was this movement that first introduced the public Bat Mitzvah celebration.