BEIRUT, Lebanon — The revolutions and revolts in the Arab world, playing out over just a few months across two continents, have proved so inspirational to so many because they offer a new sense of national identity built on the idea of citizenship.

But in the past weeks, the specter of divisions — religion in Egypt, fundamentalism in Tunisia, sect in Syria and Bahrain, clan in Libya — has threatened uprisings that once seemed to promise to resolve questions that have vexed the Arab world since the colonialism era.

From the fetid alleys of Imbaba, the Cairo neighborhood where Muslims and Christians have fought street battles, to the Syrian countryside, where a particularly deadly crackdown has raised fears of sectarian score-settling, the question of identity may help determine whether the Arab Spring flowers or withers. Can the revolts forge alternative ways to cope with the Arab world’s variety of clans, sects, ethnicities and religions?

The old examples have been largely of failure: the rule of strongmen in Egypt, Syria, Libya and Yemen; a fragile equilibrium of fractious communities in Lebanon and Iraq; the repressive paternalism of the Persian Gulf, where oil revenues are used to buy loyalty.