U.S. President Barack Obama has been pilloried for his cautious response to the Arab revolutions. One critic writing in The Post calls him "a president in full flight." Many urge the president to make a big bet in favor of democracy in the region.

When the uprisings known as the Arab Spring first began, some analysts were optimistic about the prospects for democracy, but the revolutions should be viewed in terms of decades, not seasons. Few observers in Paris in 1789 would have predicted that a Corsican corporal would lead French forces to the banks of the Nile within a decade. And interventions in the French Revolution by great powers such as Austria and Prussia fanned, rather than extinguished, the nationalist flames.

Big bets in foreign policy should have at least a reasonable prospect of success. My research of 20th-century American history has found that transformational foreign policy presidents who made big bets were not better in ethics or effectiveness.