We cannot bring back the stolen lives. We cannot bring back the lost limbs or the lost hearing. And we cannot mitigate the infinite grief of the victims' loved ones.But there is something we can and must do: We must learn all the lessons we can.

Here are some:
1. The gulf between the decent and the indecent
Tamerlan Tsarnaev, the older brother, once told an interviewer before a Golden Gloves boxing competition: "I don't have a single American friend. I don't understand them."
The reason Tsarnaev didn't understand Americans was not primarily cultural. Tsarnaev came to America when he was 14 or 15, an age when the vast majority of immigrants to America have assimilated quite successfully.

Rather, the reason was that the indecent don't understand the decent, just as the decent don't understand the indecent.

One of the greatest insights I learned as a young man came from reading Viktor Frankl's seminal work, "Man's Search for Meaning." Frankl was a Jewish psychoanalyst who survived Auschwitz, where nearly every member of his family, including his wife, was murdered. His conclusion: "There are two races of men in this world but only these two. The race of the decent man and the race of the indecent man."

Those "races" do not understand one another. But more important than understanding the indecent is overpowering and, when necessary, destroying the indecent.

2. Any religion or ideology that is above good and evil produces enormous evil.
For tens of millions of Muslims today, Islam is beyond good and evil: The infidel may be decent, but that is of no importance to the radical Islamist. For example, to become a "more religious" Muslim, Tamerlan Tsarnaev gave up boxing, marijuana, tobacco and even not wearing a shirt in the presence of females. Tsarnaev believed Islam forbade those things -- none of which is an evil. But when it came to the greatest evil -- murder (of non-Muslims) -- his religion was not only silent, it was enthusiastically supportive.

Likewise, communists in the Soviet Union, China and elsewhere -- and their many supporters in the West -- raised the creation of egalitarian society and industrialization above good and evil. And Nazism elevated race above good and evil. The environmentalists who oppose vitamin A-injected rice in the Third World place their agenda above good and evil.

Unfortunately, most religious and secular ideologues find preoccupation with human decency boring. The greatest moral idea in history, ethical monotheism, doesn't excite most people.

3. A victimhood identity produces cruelty.

The Tsarnaev brothers' primary self-perception was that of being Chechen victims, and that plus their religious convictions allowed them to blow up men, women and children with a perfectly clear conscience. Even when victimhood status is objectively true -- which it was not for these brothers, who were among the spectacularly fortunate few to be able to live in freedom and with unlimited opportunities -- nothing provides people with as good a reason to commit atrocities as does a victim mentality.

4. Happiness is a moral issue.

Happiness is not an emotional state so much as it is a moral imperative. In general, those who act happy make the world better and those who act unhappy make it worse. This is equally true in the micro and macro realms. It is not surprising, therefore, that Tamerlan Tsarnaev was described by a cousin, Zaur Tsarnaev, in this way: "He was never happy, never cheering, never smiling."

5. Boys will be bad men if they had no good men.

It is apparent that the younger brother Dzhokhar was deeply influenced by his brother, Tamerlan, who was seven years older. All of us who have an older brother, especially with a large age gap, know that he has a god-like status in the eyes of a young boy.

If good men do not inspire boys, bad men will. Without good older men in boys' lives, those boys are likely to grow up and do bad things. See our inner cities for further confirmation.

6. Universities and the left generally continue to deny any link between Muslim terrorists and their Muslim beliefs.

Just as in previous acts of Islamist terror, the left in general, and university professors in particular, continue to argue that it is wrong -- actually bigoted -- to associate these terrorists' religious beliefs with their terrorism.

Michael Eric Dyson, Georgetown professor of sociology: "So you take one part of the element, that he's Muslim. But he also might have listened to classical music. He might have had some Lil Wayne."

MSNBC host Melissa Harris- Perry: "I keep wondering is it possible that there would ever be a discussion like, 'This is because of Ben Affleck and the connection between Boston and movies about violence?' And of course, the answer is no. ... Our very sense of connection to them is this framed-up notion of, like, Islam making them something that is non-normal."

Zaheer Ali -- Harvard graduate, recipient of Columbia University's Merit Scholars Graduate Fellowship, recipient of the Social Science Research Council's Mellon Mays Pre-Doctoral Research Grant -- on MSNBC: "It isn't Muslim that is a common thing here, it's people who are alienated."
Professor Brian Levin -- director of the Center for the Study of Hate and Extremism at California State University, San Bernardino (formerly associate director of the Southern Poverty Law Center) -- to Bill Maher:

"Look, it's not like people who are Muslim who do wacky things have a monopoly on it. We have hypocrites across faiths, Jewish, Christian who say they're out for God and end up doing not so nice things."

Bill Maher's response: "That's liberal bullshit."

And that's what our children are routinely taught.
_____________________________