In the speech, President Obama demonstrated his understanding of the teachings of Christian theologian Reinhold Niebuhr. Here is the best summary of Niebuhr's thoughts on that tension that I have found.
Christians were obliged to work actively for progressive social causes and for the realization of Christian social ideals of justice and righteousness. But in doing so they had to abandon their illusions, not least in the way they thought about themselves. The pursuit of social righteousness would, he believed, inexorably involve them in acts of sin and imperfection. Not because the end justifies the means, but because that was simply the way of the world. Even the most surgical action creates collateral damage. But the Christian faith just as inexorably called its adherents to a life of perfect righteousness, a calling that gives no ultimate moral quarter to dirty hands. The result would seem to be a stark contradiction, a call to do the impossible.
And here's President Obama laying out that tension in Oslo.
We must begin by acknowledging the hard truth: We will not eradicate violent conflict in our lifetimes. There will be times when nations -- acting individually or in concert -- will find the use of force not only necessary but morally justified.
I make this statement mindful of what Martin Luther King Jr. said in this same ceremony years ago: "Violence never brings permanent peace. It solves no social problem: it merely creates new and more complicated ones." As someone who stands here as a direct consequence of Dr. King's life work, I am living testimony to the moral force of non-violence. I know there's nothing weak -- nothing passive -- nothing naïve -- in the creed and lives of Gandhi and King.
But as a head of state sworn to protect and defend my nation, I cannot be guided by their examples alone. I face the world as it is, and cannot stand idle in the face of threats to the American people. For make no mistake: Evil does exist in the world... To say that force may sometimes be necessary is not a call to cynicism -- it is a recognition of history; the imperfections of man and the limits of reason...
So yes, the instruments of war do have a role to play in preserving the peace. And yet this truth must coexist with another -- that no matter how justified, war promises human tragedy. The soldier's courage and sacrifice is full of glory, expressing devotion to country, to cause, to comrades in arms. But war itself is never glorious, and we must never trumpet it as such.
So part of our challenge is reconciling these two seemingly inreconcilable truths -- that war is sometimes necessary, and war at some level is an expression of human folly...
But we do not have to think that human nature is perfect for us to still believe that the human condition can be perfected. We do not have to live in an idealized world to still reach for those ideals that will make it a better place...
For if we lose that faith -- if we dismiss it as silly or naïve; if we divorce it from the decisions that we make on issues of war and peace -- then we lose what's best about humanity. We lose our sense of possibility. We lose our moral compass...
Let us reach for the world that ought to be -- that spark of the divine that still stirs within each of our souls.
Somewhere today, in the here and now, in the world as it is, a soldier sees he's outgunned, but stands firm to keep the peace. Somewhere today, in this world, a young protestor awaits the brutality of her government, but has the courage to march on. Somewhere today, a mother facing punishing poverty still takes the time to teach her child, scrapes together what few coins she has to send that child to school -- because she believes that a cruel world still has a place for that child's dreams.
Let us live by their example. We can acknowledge that oppression will always be with us, and still strive for justice. We can admit the intractability of depravation, and still strive for dignity. Clear-eyed, we can understand that there will be war, and still strive for peace. We can do that -- for that is the story of human progress; that's the hope of all the world; and at this moment of challenge, that must be our work here on Earth.
I suspect that we all face challenges daily that require living with that kind of tension - working to deal with the realities of the world while maintaining our belief and commitment to what is possible. Perhaps we don't see it in such stark terms as President Obama did when he approved U.S. military involvement in Libya. But his words are no less applicable to me because my sphere of influence is smaller. I can both be grateful that this country is blessed with a leader who understands this tension and use his words and actions to inspire me to hold that tension to the best of my ability.