The bloodshed in Cairo on Sunday began as a brawl between Muslims and Coptic Christians over the burning of a church in the south. But as police allegedly overreacted, the trouble came to be about opposition to Egypt's military rule.
The backdrop to the violence, however, and what threatens to fuel more, is a fundamental debate over the role of religion in governments, an issue across the lands of the Arab Spring.
In Egypt, Christians, who eagerly joined last spring's pro-democracy demonstrations, fear that their hopes for an inclusive, pluralistic state are in jeopardy from well-organised Islamic parties. Islamist factions in Libya's opposition force complain they are being shut out of a new secular government. In Tunisia, crowds have scuffled with police over a ban on wearing the niqab. Some Yemenis say Islamists are hijacking their popular uprising.
The irony is that Islamists, marginalised and excluded from political life for decades by autocratic regimes, now make secular groups and sectarian minorities fear that the Islamists themselves now hope to monopolise the political scene.
The key question everywhere is how inclusive new governments will be.
The best way to protect the idea of multiparty democracy will, we believe, be to try to be inclusive of all political forces, whether religious or secular. As with all other democracies, other branches of government and institutions must protect against any single force monopolising power.
One Arab Spring state is already experimenting along these lines. This month Tunisians will choose from among 81 parties and hundreds of independent candidates. An Islamist party, Al Nahda, leads in the polls, but only about a quarter of Tunisians say they want an Islamist government. The likely new cabinet and administration will hardly be monolithic.
At one recent campaign rally in central Tunis, hundreds of young Muslim women in head scarves joined thousands of other people to hear what one secular party had to offer them. Many of these women said what Tunisia needs now more than ever is to find a way for religious values to complement secular rule.
Such compromises are never simple, as clashes between Islamist supporters and police in Tunis this week reveal. But compromise - sharing of power - is inherent in the nature of democracy.
Voters in the Arab Spring countries will soon be answering that question.
