The invasion of Iraq and the prospect of a long occupation have raised anew the question of empire. A similar debate took place 100 years ago, in the wake of the Spanish-American War. Although the United States officially renounced the goal of being a formal imperial power like France or Britain, in practice it has long been at least quasi-imperialist.

The Founding Fathers were generally hostile to the idea of empire. Their own experience as colonial subjects naturally soured them on the idea. They also saw empire as having a corrupting influence on the mother country. In his Farewell Address, George Washington warned that imperial ambitions lead to "overgrown military establishments" that are "inauspicious to liberty" and "particularly hostile to republican liberty."

Although American leaders paid homage to Washington's warning, the westward expansion and continuing growth of America's population and economic power inevitably put strains on our adherence to the idea of "good faith and justice toward all nations ... peace and harmony with all."

By the late 1800s, there was a spirited debate in the United States about whether the nation ought to join the quest for colonies. Many argued that they were necessary in order to create markets for American goods. Arguing against this proposition, Yale economist William Graham Sumner said that colonies were a poor substitute for free trade. "Conquest can do nothing for trade except to remove the political obstacles which the conquered could not, or would not, remove. From this it follows that the only justification for territorial extension is the extension of free and enlightened policies in regard to commerce," he wrote

A few years later, the great economist Joseph Schumpeter elaborated Sumner's point that free trade obviates any benefit to colonialism. Consequently, capitalism was inherently anti-imperialist, he argued. Imperialism, in Schumpeter's view, was alien to capitalism and not its final stage, as Karl Marx had argued.

Nevertheless, the Spanish-American War left the United States an imperial power, acquiring the Philippines, Puerto Rico and Guam. Almost immediately, the United States found itself putting down native resistance in the Philippines in a bloody little conflict similar to that going on in Iraq today. This revived questions about the negative effects of imperialism.

Among those arguing this point was the great political scientist John W. Burgess of Columbia. He pointed out that it is inherently undemocratic to hold colonies. The United States must necessarily rule them in an autocratic fashion, which leads to centralized government and militarization at home. "Limited government and the colonial empire system are practically incompatible," Burgess wrote, "and unlimited government undermines democratic principle continuously and persistently."

Eventually, the urge to be a colonial power wore off, and the United States gave the Philippines their independence after World War II. However, Puerto Rico, Guam, the U.S. Virgin Islands, the Northern Marianas Islands and other territories remain de facto colonies to the present day. Continued...