One of the most puzzling things about President Obama’s foreign policy is his inconsistency. He’ll draw red lines in Syria and threaten military strikes, then call off the strikes and convene diplomatic conferences. If he’s not killing terrorists with drones, he’s bringing them to New York for civilian trial. He’ll bypass the United Nations Security Council to take military action against Syria, but demand its approval before bombing Libya.

There’s an ad hoc quality to Mr. Obama’s foreign policy. Some think he’s clever and likes to keep everyone off balance. Others attribute it to inexperience. Still others blame it on the distractions of his domestic agenda.

There’s probably truth in all these explanations. But let me suggest another partial explanation that runs a little deeper: The president is deeply conflicted about the purposes of American power. He zigzags between opposite poles because he can’t make up his mind which side is right.

Mr. Obama comes from a school of thought I call the “new liberal internationalism.” Arising with the 1960s protests against the Vietnam War, it came to dominate both the faculty lounges of America’s universities and the mainstream of the Democratic Party.

It was new in the sense that it broke with the old progressive liberalism of Woodrow Wilson and Franklin Roosevelt, which begot the Cold War liberalism of Harry Truman and John F. Kennedy. The ‘60s produced a more dovish variant, represented by the likes of George McGovern, Edward M. Kennedy, Jimmy Carter, and yes, John F. Kerry.

Its main tenet was that America had sinned; in prosecuting the Cold War, it had become an aggressive, imperialistic power. As a result, many of the world’s problems could be laid at the doorstep of American power itself.

Evidence of this world view was rife in Mr. Obama’s early days on the international stage. Witness his famous “apology” speech in Cairo and his refusal to back the Iranian demonstrators for fear of ruining negotiations with the ayatollahs. You can almost see the college professor in the newly elected Mr. Obama, gleeful at the prospect of finally being able to “speak truth to power.”

But there was a problem. Now power was in his hands. And the daily intelligence briefings of threats to America were at his fingertips. The burdens of power, and the responsibility of American lives, now lay squarely on his desk. The erstwhile student radical had no choice but to realize that America’s enemies want to kill us not because we provoke them, but because they actually hate us.

Hence the profound ambivalence: The contradiction between promising to close Guantanamo but actually further militarizing President George W. Bush’s war on terrorism with drone attacks. The talk of peace and diplomacy, yet taking America to the brink of war over Syria.

It’s hard to know which Barack Obama will show up in a crisis: The one beholden to McGovern or a clone of Mr. Bush.

Even today, the old dovish side of the new liberal internationalism is far from dead. It is alive and well in the eager embrace of new negotiations with the Iranians. Despite rhetoric to the contrary, Mr. Kerry is pursuing the same old “give peace a chance” diplomacy as secretary of state that has failed with the Iranians time and time and time again.

The “two souls” in Mr. Obama’s breast reflect the bipolarity of the new liberal internationalism. It knows America must still lead, but is unsure of how. It acknowledges the need for power, but feels conflicted and even guilty about exercising it.

This is no way for a great country’s leader to act. Maybe someday the president will manage to overcome the world view of his youth. But until he does, the country will likely be whipsawed between the president’s distrust of and obligation to the country he leads.

 - Kim R. Holmes is a distinguished fellow at the Heritage Foundation and a former assistant secretary of state.