"I believe that for all our imperfections, we are full of decency and goodness, and that the forces that divide us are not as strong as those that unite us," he said. "That's what I believe, in part because that's what a child like Christina Taylor Green believed.
"Imagine: Here was a young girl who was just becoming aware of our democracy; just beginning to understand the obligations of citizenship; just starting to glimpse the fact that someday she too might play a part in shaping her nation's future," the president said. "She saw all this through the eyes of a child, undimmed by the cynicism or vitriol that we adults all too often just take for granted."
One-by-one, Obama honored each of the six people killed, who, he said, "represented what is best in America."
Besides Christina, those killed were Judge John Roll, Dorothy Morris, Phyllis Schneck, Dorwan Stoddard and Gabe Zimmerman, the only of Giffords' staff members to perish in the shooting.
The president also praised "those who saved others" -- the nurses, doctors, policemen, staffers and bystanders who put themselves in harm's way to try and stop the shooter.
"They remind us that heroism does not require special training or physical strength. Heroism is here, all around us, in the hearts of so many of our fellow citizens, just waiting to be summoned -- as it was on Saturday morning," the president said.
Striking a tone similar to President John F. Kennedy in his 1961 inauguration speech, Obama called upon the nation to respond with charity towards one another.
"We cannot and will not be passive in the face of such violence. We should be willing to challenge old assumptions in order to lessen the prospects of violence in the future," he said. "But what we can't do is use this tragedy as one more occasion to turn on one another.
"As we discuss these issues, let each of us do so with a good dose of humility," he added. "Rather than pointing fingers or assigning blame, let us use this occasion to expand our moral imaginations, to listen to each other more carefully, to sharpen our instincts for empathy and remind ourselves of all the ways our hopes and dreams are bound together."
In perhaps the only mildly political moment of the speech, the president referenced a "discourse [that] has become so sharply polarized at a time when we are far too eager to lay the blame for all that ails the world at the feet of those who think differently than we do."
The president asked, "Rather than pointing fingers or assigning blame, let us use this occasion to expand our moral imaginations, to listen to each other more carefully, to sharpen our instincts for empathy and remind ourselves of all the ways our hopes and dreams are bound together. ... Let's make sure it's not on the usual plane of politics and point scoring and pettiness that drifts away with the next news cycle."
The president ended his speech where he began, honoring a victim: Christina Taylor Green, he said was, "so deserving of our good example ... I want us to live up to her expectations. I want our democracy to be as good as she imagined it. All of us -- we should do everything we can to make sure this country lives up to our children's expectations."