The modern Jewish movements are distinguished less by belief than by what they say about the authority of halakha, and the resulting positions are the principal fault line of contemporary Jewish life.
Orthodox and Haredi Judaism hold halakha to be divinely given and binding in its entirety. It develops, but only by the internal methods of the system, precedent, the weighing of authorities, responsa reasoning, and never in response to criteria brought in from outside it. The codes carry presumptive authority, and the burden of argument lies with anyone proposing change. Within this position there is considerable range, from the readiness of much Modern Orthodoxy to engage secular knowledge and the state to the more insulating posture of Haredi communities.
Conservative and Masorti Judaism hold that halakha is binding but has always developed historically, and that rabbinic authority may therefore adjust it in response to changed conditions. Its Committee on Jewish Law and Standards issues rulings and permits majority and minority positions to stand together, so that more than one practice may be legitimate. The 1950 responsum permitting driving to synagogue on the Sabbath where distance would otherwise prevent attendance, the decisions of the 1980s admitting women to ordination, and the 2006 papers on the status of gay and lesbian Jews are the cases usually cited, by supporters as evidence of a living legal system and by critics as evidence that the criteria have become external.
Reform and Liberal Judaism hold the ethical and monotheistic content of the tradition to be binding and, in classical Reform, treated the ritual law as no longer obligatory; the operative principle is the informed autonomy of the individual. Later Reform thought, from the mid-twentieth century onward, has recovered a great deal of ritual practice, but as chosen rather than commanded.
Reconstructionist Judaism, following Mordecai Kaplan, holds that Judaism is an evolving religious civilisation rather than a revealed law, and that the tradition "has a vote, not a veto". Practice is arrived at communally, and inherited observance is valued as the civilisation's accumulated expression rather than obeyed as command.
These are not merely theoretical differences. Because conversion, marriage and divorce are governed by halakha, disagreement about its authority produces disagreement about personal status, and the movements do not uniformly recognise one another's decisions, a practical problem that has occupied Jewish communal and Israeli political life for decades.