“Throughout American history, there have been moments that call on us to meet the challenges of an uncertain world, and pay whatever price is required to secure our freedom. They are the soul-trying times our forbearers spoke of, when the ease of complacency and self-interest must give way to the more difficult task of rendering judgment on what is best for the nation and for posterity, and then acting on that judgment — making the hard choices and sacrifices necessary to uphold our most deeply held values and ideals. This was true for those who went to Lexington and Concord. It was true for those who lie buried at Gettysburg. It was true for those who built democracy’s arsenal to vanquish fascism, and who then built a series of alliances and a world order that would ultimately defeat communism. And this has been true for those of us who looked on the rubble and ashes of 9/11, and made a solemn pledge that such an atrocity would never again happen on United States soil; that we would do whatever it took to hunt down those responsible, and use every tool at our disposal – diplomatic, economic, and military — to root out both the agents of terrorism and the conditions that helped breed it.”

Quotes, IPI speech (2000)
Context: The disruption of the world's ecological systems — from the rise of global warming and the consequent damage to our climate balance, to the loss of living species and the depletion of ocean fisheries and forest habitats — continues at a frightening rate. Practically every day, it becomes clearer to us that must act now to protect our Earth, while preserving and creating jobs for our people.
And at the very same time that these threats are developing, the traditional nation-state itself is changing — as power moves upwards and downwards, to everything from supra-national organizations and coalitions all the way down to feuding clans. Susceptible to tyrants willing to exploit ethnic and religious rivalries, the weakest of these states have either imploded into civil war or threatened to lash out across their borders.
To meet these challenges requires cooperation on a scale not seen before. A realistic reading of the world today demands reinvigorated international and regional institutions. It demands that we confront threats before they spiral out of the control. And it requires American leadership — to protect our interests and uphold our values.

1960, Sport at the New Frontier: The Soft American

About selecting federal judicial candidates.
Speech to American Enterprise Institute (January 17, 2007)

May 1961 in address to joint session of congress https://www.jfklibrary.org/learn/about-jfk/historic-speeches/address-to-joint-session-of-congress-may-25-196125
1961

Source: The Christian Agnostic (1965), p.77-78, (Paul Tillich: The Shaking of the Foundations. 1963. Pelican Books. p. 164

2000s, 2001, First inaugural address (January 2001)

For the American people can no more meet the demands of today’s world by acting alone than American soldiers could have met the forces of fascism or communism with muskets and militias. No single person can train all the math and science teachers we’ll need to equip our children for the future, or build the roads and networks and research labs that will bring new jobs and businesses to our shores. Now, more than ever, we must do these things together, as one nation and one people.
2013, Second Inaugural Address (January 2013)

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The Zürau Aphorisms (1917 - 1918)

Barack Obama’s Remarks in St. Paul http://www.nytimes.com/2008/06/03/us/politics/03text-obama.html (3 June 2008)
2008