Progressive revelation holds that religious truth is relative rather than absolute — each Manifestation brings the measure of teaching an age can receive, and social laws in particular are framed for a specific time and are expected to be superseded, while the spiritual essence is constant. That is what allows the faith to say that all the great religions are true without having to reconcile their laws. The important limiting clause is often missed: Bahá'u'lláh set a floor of one thousand years before another Manifestation may appear, and stated that anyone advancing such a claim before the expiry of a full thousand years is a liar. This is a deliberate anti-fragmentation device — it forecloses the standard route by which charismatic movements split — and combined with the written Covenant it accounts for the near-total absence of Bahá'í sects. The corollary is that the Bahá'í dispensation itself expects to be superseded eventually, which is an unusual thing for a religion to build into its own doctrine.