Western theorists of the political and social sciences have typically held that increasing secularism is an inevitable feature of modern nation-states. Some states may be openly hostile to any expression of religion as a factor in public affairs; others tend to reduce religious life to the realm of nothing more than individual, discretionary, personal behavior in a few compartmentalized areas of activity to which the state is indifferent. The Iranian Revolution of 1979 –80 demonstrated beyond question that Iran, despite fi fty years of secularizing reform under the Pahlavi regime, would not conform to this model. The Islamic Republic of Iran is as thoroughly a theocratic state as one could imagine apart from the Vatican or a Tibet under the Dalai Lama. The constitution itself confi rms that all sovereignty belongs to God, recognizes the Twelver ( Esnâ ‘ ashari; also called Ja’fari or Emâmi / Imami) school of Shi‘ite Islam as the offi cial religion, specifi es that the state exists in order to promote a favorable environment for religion, vests the highest executive authority in representatives of the Shi‘ite ‘ olamâ (professional religious scholars), and requires that “all civil, penal, financial , economic, administrative, cultural, military, political, and other laws and regulations must be based on Islamic criteria.”

There is thus virtually no aspect of the culture and customs of Iran—be it law, social customs, festivals and holidays, art, architecture, or even dress and diet—that lacks a religious dimension of some kind, and these will be examined as appropriate in other chapters of this book. The purpose of this chapter is to survey the development of key religious ideas, practices, and institutions that have played an important role throughout Iranian history, with a particular emphasis on those specific to its main contemporary religion, Shi‘ite Islam.