Last week's terrorist attack in Boston -- which killed three, including an 8-year-old boy, and badly injured dozens of others -- served as a grim reminder of the evil that exists in our world. Since Sept. 11, Americans have been largely immune from attacks by terrorists. But for many of us, the days of color-coded terror warnings and armed guards in airports seem like relics of another era. The Boston bombings should be a rude awakening to us all that the existence of evil, whatever its source may be, is real.

The Boston Marathon attack was also a reminder of the great good in the world -- of the humanity and acts of kindness that were shown to the victims who suffered horrible injuries, all the participants in the marathon and the residents and neighbors of Boston. We saw the goodness in the first responders who fearlessly risked their lives to help and in the outpouring of support and compassion from across the United States and across the world that followed the news of the attack. In those first moments and even now -- as we wait to learn more -- the good in the world prevailed and is prevailing.

This has come in many forms. The Red Cross, for example, tweeted that it did not need more blood, because so many people wanted to donate in the hours after the attack that volunteers had to encourage people to come back later. First responders -- as well as former New England Patriots player Joe Andruzzi and a man named Carlos Arredondo, the "cowboy hat guy" -- risked their lives by running toward the explosion, rather than away from it, to apply tourniquets and ease the pain of the wounded.

And of course, the police and medical personnel stepped up when needed and did their jobs like the professionals they are. The good extends across the world in the donations, offers of assistance and small gestures that many millions have made. As much as the attack may have rattled our faith in humanity, the pictures and stories of compassion coming out of Boston should only make our faith in the goodness of the world stronger.

The good and evil on display in Boston are more than just something to observe. They're something we should take to heart, a lesson to live our lives by -- and one that puts good above evil. We can protect the good by showing these great examples to our children and by living lives that set those examples every day. This starts in our families, in our churches, in our schools and in our communities. Acts of goodness and kindness and compassion can be taught, and it's up to us to see that they are. And it is important to note that these institutions that help us create good need to be protected.

As long as we live in this dangerous world, we must take actions to keep ourselves safe. Whether the threats are from known enemies from abroad or from mentally disturbed Americans, we need strong intervention. We can't afford to cut resources to our military, and we can't afford to neglect alienated young men, who are the source of nearly all of these kinds of attacks. And we must not be afraid to call evil by its name. America does not have sympathy for the cowards who inflict death and pain on innocents, and we should support their prosecution and punishment.

Evil struck last week at an event that was surrounded by good, where families and friends cheered on runners and awaited them at the finish line. The race was not in a war zone. It was a sporting event and a community event. The contrast between good and evil could not be starker. But there it was -- evil -- in plain view for us all to see.

God bless those whose lives were lost or permanently changed last week. You did nothing to deserve this. And God bless the first responders and the people of Boston who stepped up to remind us all of the resilience, of the humanity and of the good that exist. If we do our part as Americans to protect that, this spirit will prevail at home and abroad.