And yet, it cannot be said that John F. Kennedy lived an easy life. He lost an older brother in the war; a sister shortly thereafter. He nearly lost his own life, too, when a Japanese gunship cut his PT boat in half, casting him into the water, from which he swam a crewmate to safety. Another sister struggled with a severe mental handicap. His own health was so poor that priests pronounced his last rites on several different occasions. And he endured the personal prejudice and political poison of anti-Catholic fervor.

And there is surely a possibility, under such circumstances, that a person will retreat from the world; that a person, particularly one born to wealth, will seek a life of luxury and ease; that a person, confronted by the coldness of chance, will become bitter or cynical or small. It has happened to others.

But that is not the life that John F. Kennedy chose. As he famously said at a press conference, “l(fā)ife is unfair.” We can’t choose the lots we are given in life, but we can choose how to live that life. John F. Kennedy chose a life in the arena, full of confidence that our country could surmount any obstacle, as he’d seen it do himself. He chose a life of leadership, fired not by na?ve optimism, but committed realism; “idealism,” as his wife Jackie put it, “without illusions.” That is the idealism -– soaring but sober –- that inspired the country and the world one half century ago.

I can only imagine how he must have felt, entering the Oval Office in turbulent times. (Laughter and applause.) The Soviet Premier, Khrushchev, had threatened to “bury” America just a few years before. Wars of Liberation, as they were called, were being waged around the globe -– from Laos and Vietnam to Congo and Cuba, just 90 miles from our shore. At home, a young preacher’s cause was gaining traction across a segregated land.

In this volatile America, this tinderbox of a world, President Kennedy led with a steadying hand, defusing the most perilous crisis of the Cold War without firing a single shot. Enforcing the rights of young black men and women to attend the university of their choice. Launching a corps of volunteers as ambassadors for peace in distant centers of the globe. Setting America’s sights on the moon, unwilling to lose the Space Race in the wake of Sputnik.

We know the moon-shot story. It’s a familiar one, often invoked to make the case for an ambitious idea. But it’s easy to lose sight of just how improbable it seemed in May of 1961. When President Kennedy proposed going to the moon, America had just 15 minutes of manned flight experience in space. NASA had neither a plan nor a shuttle for making a lunar voyage. (Laughter.) Its own engineers had taken out the slide rules, and they were deeply skeptical of the mission. (Laughter.)

The science just wasn’t there. President Kennedy understood that. But he also knew something else. He knew that we, as a people, can do big things. We can reach great heights. We can rise to any challenge, so long as we’re willing to ask what we can do for our country; so long as we’re willing to take America’s destiny into our own hands. What President Kennedy understood was the character of the people he led: our resilience, our fearlessness, our distinctly American ability, revealed time and again throughout history, to defy the odds, to fashion our future, to make the world anew.

The world is very different now than it was in 1961. We face new trials and new uncertainties, from our economy to our security. We have a politics that can often seem too small for the hardships at hand. So meeting these tests won’t be easy. But we cannot forget, we are the heirs of this President, who showed us what is possible. Because of his vision, more people prospered; more people served; our union was made more perfect. Because of that vision, I can stand here tonight as President of the United States. (Applause.)

So John F. Kennedy captured that American spirit that not only put a man on the moon, but saved a continent from tyranny and overcame a Great Depression; that forged, from 13 colonies, the last best hope on Earth. And if we can hold onto that spirit today, I know that our generation will answer its call as ably as earlier ones did before us.

In December 1962, President Kennedy was asked by the Saturday Evening Post to submit his favorite quotation. A student not only of history, but also of literature, he chose a passage written by the poet Oliver Wendell Holmes, Sr., father of the Supreme Court justice. Mr. Holmes wrote:

“I find the great things in this world -- is not so much where we stand, as in what direction we are moving: to reach the port of heaven, we must sail sometimes with the wind and sometimes against it -– but we must sail, and not drift, nor lie at anchor.”