“When E.F. Hutton talks,” the famous TV ads for the financial firm once declared, “people listen.” No one is going to make TV ads on his behalf, but the same deserves to be said of Harvard scholar Samuel Huntington, the most important political scientist in America. His last book, “The Clash of Civilizations,” forecast the civilizational tensions that became obvious to everyone in the post-9/11 world. When Huntington writes, people listen — or they should.

Huntington’s prodigious credibility makes his warning of the possible end of the United States as we know it in his new book, “Who Are We?,” all the more alarming.

Huntington sees an America gripped in a “crisis of national identity.” What is that identity? It is partly based on what Huntington calls The Creed, our belief in liberty, democracy, individual rights, etc. But The Creed has a particular source: America’s Anglo-Protestant culture, which includes “the English language; Christianity; religious commitment; English concepts of the rule of law, the responsibility of rulers, and the rights of individuals; and dissenting Protestant values of individualism, the work ethic, and the belief that humans have the ability and the duty to try to create heaven on earth, a ‘city on the hill.'”

This culture forged a country where people from across the world could arrive and become rich, happy and free — if they assimilated. Huntington writes, “Throughout American history, people who were not white Anglo-Saxon Protestants have become Americans by adopting America’s Anglo-Protestant culture and political values.” He notes that this is “an argument for the importance of Anglo-Protestant culture, not for the importance of Anglo-Protestant people.”

But Anglo-Protestant culture has taken a pounding during the past three decades. From multiculturalism, which rejects the idea of a dominant culture. From the assertion of group identities based on race, ethnicity and gender. And from “denationalized” elites, hostile to America’s culture and determined to weaken it in myriad ways. All these forces have weakened the nation’s ability to assimilate immigrants. Feeling less pressure to learn English or naturalize, the new, largely Mexican and Hispanic immigrants have been able to establish unassimilated ethnic enclaves.

Huntington hopes for a better future — for the sake of all of us. “Americans should,” he writes, “recommit themselves to the Anglo-Protestant culture, traditions, and values that for three and a half centuries have been embraced by Americans of all races, ethnicities, and religions and that have been the source of their liberty, unity, power, prosperity, and moral leadership as a force for good in the world.”

A world of grief awaits Huntington. He will inevitably be misunderstood and smeared. Already, a writer in Time magazine has suggested that Huntington’s book should have gone unwritten. On the contrary, only a writer of Huntington’s stature has a chance to punch through the oppressive pieties surrounding these issues and force a forthright debate of them. Huntington says he undertook his new book in the spirit of “a patriot and scholar.” A courageous one.