ON A FRIDAY the U.S. president was killed by an assassin. On Monday he was buried. On Thursday the country held its annual feast of Thanksgiving. To someone from another country, that might seem an incongruous, if not inappropriate, series of events, but in fact it was in keeping with one of our most unbreakable traditions.

Thanksgiving was proclaimed a national holiday by Abraham Lincoln when the United States was in its deepest distress, a century before John F. Kennedy’s death. After two years and more of a bloody Civil War, it seemed possible that new leaders would be elected who would accept the secession of the Southern states. But the Union held through the election and the war and then through Lincoln’s murder.

Afterward, over a century, the country lost three more presidents to assassination: Garfield, McKinley, Kennedy. None of the killers seems to have signified anything larger than his own delusions. The peace was kept each time, and the republic went on its way, however contentiously.

This hasn’t always been the case elsewhere in the world. In 1914 the killing of an Austrian prince by an assassin with ties to a hostile country helped turn old hatreds and rivalries into a catastrophic world war. In 1938 the murder of a German diplomat by a distraught Jewish gunman provided the pretext for Nazi Germany to begin its racial war of extermination. Less than two decades ago, the assassination of two African presidents was followed by the massacre of hundreds of thousands of Rwandans.

The United States was not entirely at peace in Kennedy’s time — it rarely is. There were some ugly, spontaneous scenes of celebration just after his death, mostly in the South and mostly stemming from another proclamation by Lincoln, having to do with the American promise of equality and delivered at Gettysburg a century before Kennedy’s death, almost to the day. Yet the assassination of Kennedy was followed not by upheaval or strife but by new and effective civil rights legislation — advanced by the fallen president’s successor, Lyndon Johnson, and passed by bipartisan majorities — that fulfilled much of Lincoln’s century-old vision and went beyond it in many ways.

Thanksgiving, since its earliest days, long before the nation’s founding, has been not so much about plenty and good fortune as about survival. It has been a time for focusing on the essentials of our common existence and what is necessary to maintain them — for an acknowledgment of what holds a country together.

“Since last Friday, Americans have turned to the good, to the decent values of our life,” Lyndon Johnson said in his 1963 Thanksgiving address. “These have served us. Yes, these have saved us. The service of our public institutions and our public men is the salvation of us all, from the Supreme Court to the States. And how much better would it be, how much more sane it would be, how much more decent and American it would be if all Americans could spend their fortunes and could give their time and spend their energies helping our system and its servants to solve your problems instead of pouring out the venom and the hate that stalemate us in progress.”