CAIRO  The future of the Arab world, perched between revolt and the contempt of a crumbling order, was fought for in the streets of downtown Cairo on Wednesday.

Tens of thousands of protesters who have reimagined the very notion of citizenship in a tumultuous week of defiance proclaimed with sticks, home-made bombs and a shower of rocks that they would not surrender their revolution to the full brunt of an authoritarian government that answered their calls for change with violence.

The Arab world watched a moment that suggested it would never be the same again  and waited to see whether protest or crackdown would win the day. Words like “uprising” and “revolution” only hint at the scale of events in Egypt, which have already reverberated across Yemen, Jordan, Syria and even Saudi Arabia, offering a new template for change in a region that long reeled from its own sense of stagnation. “Every Egyptian understands now,” said Magdi al-Sayyid, one of the protesters.

The protesters have spoken for themselves to a government that, like many across the Middle East, treated them as a nuisance. For years, pundits have predicted that Islamists would be the force that toppled governments across the Arab world. But so far, they have been submerged in an outpouring of popular dissent that speaks to a unity of message, however fleeting  itself a sea change in the region’s political landscape. In the vast panorama of Tahrir Square on Wednesday, Egyptians were stationed at makeshift barricades, belying pat dismissals of the power of the Arab street.