“Ideas, passionately promoted and put to the test—that’s what politics can be. That’s what our country can be…It can be a confident America, where we have a basic faith in politics and leaders. It can be a place where we’ve earned that faith. All of us as leaders can hold ourselves to the highest standards of integrity and decency. Instead of playing to your anxieties, we can appeal to your aspirations. Instead of playing the identity politics of “our base” and “their base,” we unite people around ideas and principles. And instead of being timid, we go bold.”

2010s, 2015, Presidential Bid Announcement (June 16, 2015)

2014, Address to European Youth (March 2014)
Context: In the end, the success of our ideals comes down to us -- including the example of our own lives, our own societies. We know that there will always be intolerance. But instead of fearing the immigrant, we can welcome him. We can insist on policies that benefit the many, not just the few; that an age of globalization and dizzying change opens the door of opportunity to the marginalized, and not just a privileged few. Instead of targeting our gay and lesbian brothers and sisters, we can use our laws to protect their rights. Instead of defining ourselves in opposition to others, we can affirm the aspirations that we hold in common. That’s what will make America strong. That’s what will make Europe strong. That’s what makes us who we are. And just as we meet our responsibilities as individuals, we must be prepared to meet them as nations. Because we live in a world in which our ideals are going to be challenged again and again by forces that would drag us back into conflict or corruption. We can’t count on others to rise to meet those tests.

"In the long history of the world, only a few generations have been granted the role of defending freedom in its hour of maximum danger. I do not shrink from this responsibility — I welcome it." is one of seven quotes inscribed on the walls at the gravesite of John F. Kennedy at Arlington National Cemetery.
"The energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it — and the glow from that fire can truly light the world." is one of seven quotes inscribed on the walls at the gravesite of John F. Kennedy at Arlington National Cemetery.
"And so, my fellow Americans: ask not what your country can do for you — ask what you can do for your country. My fellow citizens of the world: ask not what America will do for you, but what together we can do for the freedom of man." is one of seven quotes inscribed on the walls at the gravesite of John F. Kennedy at Arlington National Cemetery.
It has been reported at various places on the internet that in JFK's Inaugural address, the famous line "Ask not what your country can do for you, ask what you can do for your country", was inspired by, or even a direct quotation of the famous and much esteemed writer and poet Khalil Gibran. Gibran in 1925 wrote in Arabic a line that has been translated as:
::Are you a politician asking what your country can do for you or a zealous one asking what you can do for your country?
::If you are the first, then you are a parasite; if the second, then you are an oasis in a desert.
However, this translation of Gibran is one that occurred over a decade after Kennedy's 1961 speech, appearing in A Third Treasury of Kahlil Gibran (1975) edited by Andrew Dib Sherfan, and the translator most likely drew upon Kennedy's famous words in expressing Gibran's prior ideas. For a further discussion regarding the quote see here.
1961, Inaugural Address
Context: In the long history of the world, only a few generations have been granted the role of defending freedom in its hour of maximum danger. I do not shrink from this responsibility — I welcome it. I do not believe that any of us would exchange places with any other people or any other generation. The energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it — and the glow from that fire can truly light the world.
And so, my fellow Americans: ask not what your country can do for you — ask what you can do for your country.
My fellow citizens of the world: ask not what America will do for you, but what together we can do for the freedom of man.

2015, State of the Union Address (January 2015)

Tennessee True Values Tour remarks, Jackson, Tennessee (4 February 2004) http://www.clark04.com/speeches/040/

2015, Naturalization Ceremony speech (December 2015)

2007

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2000s, Promises to Keep (2008)