Honoring the victims of the Tucson massacre, President Obama on Wednesday urged Americans to resist turning on each other in anger, but instead talk "in a way that heals." Directly confronting the agonized and at times piercing public debates that have followed last weekend's attack, Obama aimed to diffuse some of the bitterness, saying it was not a "lack of civility" that led to the rampage.

"If this tragedy prompts reflection and debate, as it should, let's make sure it's worthy of those we have lost," Obama said. "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."

In remarks that were at turns somber, rousing and defiant at a memorial service at the University of Arizona's McKale Memorial Center, Obama made mention of all six people killed among the 20 who were shot at a community event hosted by Democratic Rep. Gabrielle Giffords.

Obama and First Lady Michelle Obama spent an afternoon before the service visiting with the families of the victims and with Giffords, who remains hospitalized in critical condition after being shot in the head by a lone gunman, and who, the president said, opened her eyes for the first time since the shooting.

Repeatedly referring to "Gabby," Obama said, "I can tell you this -- she knows we're here and she knows we love her and she knows that we will be rooting for her throughout what will be a difficult journey."

For the president, Wednesday's memorial carried a heavy burden. Called on to make sense of incomprehensible violence, Obama offered a unifying message, saying "our hearts are broken -- and yet, our hearts also have reason for fullness."

A parent of two young daughters, Obama earlier this week mentioned how the incident affected him as a father, saying he kept thinking of the families.

In that same spirit, he lingered in his remarks over the youngest victim of Saturday's violence, 9-year-old Christina Green.

"In Christina we see all of our children," Obama said. "So curious, so trusting, so energetic and full of magic."

It is adults, he said, who have become jaded by cynicism and vitriol in public debate. Green, he said, had higher expectations -- and called on adults to live up to them.

"If there are rain puddles in heaven, Christina is jumping in them today," he said.

The president, an infrequent churchgoer who rarely invokes his Protestant beliefs in his public duties, in this instance quoted Scripture and told his audience, "I pray with you."

Obama called on Americans to pay tribute to Green and the other victims by remembering the democratic spirit that values debate and questioning ideas "without questioning each other's love of country."

Like his predecessors who confronted tragedy by urging Americans to consider their better natures, Obama said the issues currently dividing Americans -- politics, gun control, the treatment of mental illness -- are "not as strong as those that unite us."

"I believe we can be better," Obama said. "Those who died here, those who saved lives here -- they help me believe."

"We may not be able to stop all evil in the world," he said. "But I know that how we treat one another is entirely up to us. I believe that for all our imperfections, we are full of decency and goodness."