Sometimes it takes a while before it all sinks in.

Now, on the 13th anniversary of the Sept. 11, 2001 terrorist attacks on America, maybe we can finally reflect upon the horror and try to learn something from the tragedy.

At Nichol’s deli counter a couple weeks ago I bumped into Donna Marsh O’Connor – the former Liverpool Central School District Board of Education member. We chatted about her work, teaching writing and rhetoric at Syracuse University, and about her husband’s book-in-progress.

In casual conversation — out of a curious mix of courtesy and dread — we ignore the elephant stomping around the room. So we did not discuss the tragedy that casts a long shadow over Donna’s life: she lost her 29-year-old daughter, Vanessa, at World Trade Center Tower 2 on Sept. 11, 2001.

While most Americans craved revenge on al-Qaeda, Donna has worked hard to dispel the desire for vengeance.

A personal loss

Last year, Donna penned a poignant essay for the Huffington Post, writing in part:

“Today is a dozen years since I lost my baby girl as she ran from the falling towers of the [building] then called World Trade Center. She, full of life and with the life of our future held within her womb, was crushed by the matter and the matters that fell. Five minutes late and 10 feet from an alley that would have meant the rest of our lives.

“How many firefighters and first responders lost their lives that day and since? Three hundred forty three firefighters that day alone. And in the years since – countless. They are still dying.

How many lost their lives because of that morning — our military service people, our first responders, innocent civilians in Afghanistan and Iraq? For what? What has been accomplished in the years since that have for a kinder globe for anyone?

“A dozen years. How many pounds of flesh? Can lives be measured in such a way ever? In quantity? In number? How many people? How many died or, like me, lost forever the lives they once occupied in exchange for this one, this one filled with grief and worry forever that it will happen again?

“No one can ever answer. Nor should they try.

“Know this: My baby girl — Vanessa Lang Langer — mattered. She changed so many lives and she taught me that quantity, no matter how measured by any means, can never account for the slightest love. And mine for her right now is massive.

“Under any circumstances, we must not continue the wars began in her name and in the names of those countless and uncountable who surely left broken hearts and souls to mourn here on Earth.

“And we must not start more war. No more bombs. Never in the name of peace. On 9/11/2013, a dozen years post, let us surprise ourselves. Let us choose kindness and peace and remember that we are here to experience the joys of touching with our bodies other bodies. We destroy that to what unquantifiable end? To what matter of destruction of our souls?”

‘Beyond Tolerance’

One of America’s most respected theological journalists, Gustav Niebuhr, will explore the religious ramifications of the 2001 attacks at 7 p.m. Thursday Sept. 11, at the Liverpool Public Library.

Niebuhr¬’s great-uncle, Reinhold Niebuhr, authored the famous Serenity Prayer and taught at New York’s Union Theological Seminary. His grandfather, H. Richard Niebuhr, taught at Yale Divinity School and his father, Richard Niebuhr, taught theology at Harvard Divinity School.

Journey of discovery

After the Islamic jihadists crashed those jets into the World Trade Center, the Pentagon and a field in Pennsylvania in 2001, Gustav Niebuhr embarked on a journey of discovery.

At a time when most Americans craved revenge, Niebuhr found more positive responses across the country. While religious conflict dominated the media, Niebuhr talked with Buddhists, Catholics, Jews, Baptists, Muslims and Episcopalians across America, men and women who were building, not burning, the bridges between faiths. His 2008 book, “Beyond Tolerance,” reveals his findings.

In 2004, Niebuhr was hired as an associate professor in religion and the media at Syracuse University, a dual appointment in the department of religion and the S.I. Newhouse School of Public Communications, since 2004.

The 58-year-old professor, who received degrees in history from Pomona College in California and Oxford University, said history remains his passion. “You cannot understand the history of America,” he said, “without understanding religious history.”