The man sat in the sun outside the St. Paul coffee shop wearing a white ball cap, loose-fitting sweat clothes and shiny white sneakers. His head was down, and his eyes were fixed on an open paperback book. He held a pencil and occasionally looked up from his reading as if to pluck an answer from the sky, then jotted something down.

A passerby might have taken the man for someone on his way to the gym, which he was, or perhaps a retiree working on a puzzle book, which, in a way, he was.

The book, however, was called "The Strange World of Quantum Mechanics," and the puzzle was the same one Thomas Sullivan had been trying to answer all his life, and that is: What is life?

I'm certain I phrased that much too simply because Sullivan employs the skills of a diamond cutter in his use of words to explain what he has done for a living for 45 years, which is to consider the Big Picture questions of life and try to make sense of them. God. Evil. Existence. Truth.

Most of us have thought that pondering the meaning of life for an hour was a waste of an hour, and it's probably so. But to spend a life asking that question? That's different, and it becomes keenly apparent after 10 minutes of talking to Sullivan.

Meet the philosopher in repose. After 45 years of teaching philosophy at the University of St. Thomas, Sullivan is stepping down, but not giving up a quest he started as a young boy.

The child of a secret marriage by a Catholic dad and Jewish mom, Sullivan was raised in a religious void. He had several revelatory moments along the way, including becoming a devout Catholic. His choice of philosophy was a "combination of situations and odd events" that he has now come to think of as providence.

"I was puzzled in elementary school about things such as mathematics," said Sullivan. "If they said, 'take three and four and add them together,' I'd say, take three from where? It was kind of an impediment, because when they started talking about negative numbers I about went over the edge. Everything to me seemed to take on a hue that others didn't see or care about.

"The finitude of all activities bothered me to no end," he said. "People would strive, hit a certain pace and then die wretched deaths after lives that are generally immensely disappointing."

Sullivan recalls vividly a woman in a nearby apartment in Chicago dying painfully of cancer who would wail into the night asking God to take her. "These things weighed on my mind," he said.

He thought of becoming a fireman, like his father, but mostly because it would give him time to read. Instead, he chose teaching over becoming a priest, then carved out a stellar career of the mind over the next four decades, trying to make Thomas Aquinas relate to the real world, getting befuddled by Ludwig Wittgenstein.

Becky Lentz, a longtime neighbor of Sullivan's, recalled how he would gather up his six children and neighborhood kids, and give them a mental puzzle to solve. "Dr. Sullivan is the kindest, smartest man I know, and he changed the way I thought about the world," said Lentz.

Sandra Menssen, a colleague in the Philosophy Department, said that students and faculty sought Sullivan out as a mentor. She recalls a former student who approached them at a pizza place to tell Sullivan: "You won't remember me; I was an advisee of yours many years ago at St. Thomas. I just had to come over and tell you that you changed my life!"

Yet, Sullivan claims to have given the worst job interview in the history of St. Thomas, partly because he was ill, "but they took a chance and it turned out pretty well after that."

Talking with Sullivan about the existence of God and the nature of good for two hours can make a guy feel pretty small, but he's so unassuming it's painless. He told a particularly funny story about arguing with two other philosophers about God at a bar. "It got about as loud as three philosophers can get," he said. Obviously, Sullivan remains devoutly faithful.

"Along the way, I have lost a lot of confidence in what the human mind can do without assistance from revelation, particularly in the area of morals. It's hard to make a case for absolute human decency on secular grounds. Although most of us, when we are thinking about terrorism, heartily condemn targeting the innocent, we tend to see things differently when it comes to firing off nuclear weapons in retaliation. Else, why hold these weapons of mass destruction? When we reflect on secular reasons for staying our own hand, not much that is philosophically defensible comes to mind. If we do hesitate to approve of securing the death of the innocent no matter what, it is likely because we think the Ten Commandments forbids it, even if the going gets rough."

Socrates said "the unexamined life is not worth living."

Is it?

"Yes," said Sullivan. "You might be better off for it. A lot of people live wonderful lives following their better instincts. It might be impossible for some of us to lead an unexamined life, however. I still wonder where the number three is." • 612-673-1702