The problem is that the attempt to disengage, to claim that the United States need not take sides in the conflict between Sunnis and Shiites or generals and Islamists, only leads back to the same cycle of passivity and ad-hoc reaction in which Obama is now stuck. That’s partly because, as the last month has demonstrated, a stand-back policy can’t hold when more than 600 unarmed protestors are gunned down in a single day in Cairo, or when 1,400 civilians are suffocated by sarin gas outside Damascus. A failure to respond by the only outside power capable of making a difference only invites greater crimes and worse threats to vital U.S. interests.

More to the point, inaction is a way of supporting a side — usually the wrong one. U.S. aid still flows to the Egyptian armed forces while their persecution spreads from Islamists to secular journalists and liberal democrats. The Sunni regime in Bahrain uses U.S.-supplied weapons to suppress a Shiite uprising. And clinging to the sidelines in Syria cedes the battlefield to Assad, Iran and al-Qaeda.

At the root of Obama’s foreign policy dysfunction is a refusal to accept that an American president must take on the history that erupts on his watch — whether it is the fall of the Berlin Wall, the attacks of Sept. 11, 2001, or the Arab revolutions — and use his unique power to shape it. It’s no use lamenting that this is not where he wants to spend his time or that the public isn’t interested. In the end, he will be obliged to act; the question is whether he will drive events, or they him.