tawhid [oneness of God], nubuwwat [prophethood of the Prophet Muhammad (s)], and resurrection are the three main principles of Islam. All Islamic sects believe in these three principles; but each one has special principles which separate it from other sects. For the Shi'a, 'adl [justice of God] and imamate are the additional principles.

Believing in the principles of religion is obligatory; but there is disagreement as to whether certainty of the principles is required or supposition is enough. Also there is discussion over the sufficiency of believing in the principles of religion out of emulation (taqlid).