President Obama in Havana on Tuesday. (Jeffrey Arguedas/European Pressphoto Association)

PRESIDENT OBAMA concluded his groundbreaking trip to Cuba with a speech to the island’s people that celebrated democracy in the presence of Raúl Castro, leader of a decaying system of authoritarianism and control. A bright future for Cuba, Mr. Obama declared, “depends on the free and open exchange of ideas.” He said that “citizens should be free to speak their mind without fear,” and free “to organize, and to criticize their government, and to protest peacefully, and that the rule of law should not include arbitrary detentions of people who exercise those rights.” He added, “And yes, I believe voters should be able to choose their governments in free and democratic elections.” None of this exists in today’s Cuba, and the real question about Mr. Obama’s thaw with the nation is whether serious change will come any sooner — or at all — because of his rapprochement.

Mr. Obama admonished Mr. Castro, “You need not fear the different voices of the Cuban people — and their capacity to speak, and assemble, and vote for their leaders.” He described American democracy as imperfect but reminded the Cuban people and their ruler that its strength is open debate. “It’s healthy,” he said. “I’m not afraid of it.” Mr. Castro clearly is.

Mr. Obama met privately with a group of dissidents, many of whom have felt the United States ignored them in recent months as it made concession after concession without winning any reduction in Cuba’s assault on human rights. Among those he met were Berta Soler, leader of the Ladies in White, a group that was formed by relatives of victims of a regime crackdown more than a decade ago, and Antonio Rodiles, a courageous exponent of democracy who has been detained and beaten for his views. Dozens of other political dissenters were not present because they are still in prison.

A truculent Mr. Castro responded to a serious question about political prisoners by asking , “What political prisoners?” Before Mr. Obama arrived, protesters were again detained; the Internet remains highly restricted; political plurality does not exist.

Mr. Obama insisted he was not seeking regime change, hailed Cuba’s education and health systems and lavished praise on Cuba’s entrepreneurs. He left much unsaid about the overweening socialist system, the ubiquitous secret police and the regime that still dominates so much of Cuban life. Will the regime be enhanced or undermined by Mr. Obama’s policy shift? Does the effective end of the embargo give a lift to Cuba’s rulers, or infect the population with a yearning to throw off the suffocating diktat? The real test of Mr. Obama’s thaw is not to be found in the pomp and circumstance of his visit, but in whether it leads to a Cuba that is freer and more open after Air Force One has departed.