The only UFO I ever saw was when I was standing under the stars with Maddy about 10 years ago. Maddy was mad for UFOs. To her, it just made sense that out in the depths of space would be intelligent life. No less a luminary than Carl Sagan – and before him Frank Drake and lately Stephen Hawking – have employed the same reasoning.

If you do the math (Dr. Sagan was famous for marveling at the “bill-yuns and bill-yuns” of galaxies), it is difficult to believe that there aren’t other forms of intelligence in the universe. In 1961, Dr. Drake, the father of the Search for Extraterrestrial Intelligence project, came up with an equation to show how probable intelligent life is.

Maddy was no cosmologist. She was an amateur UFO watcher like thousands of others around the globe. She loved sitting in a chair overlooking the North Atlantic and peering into the glorious night sky. What do I think of UFOs? I am a skeptic.

Journalists are professional doubters. Unveiling a government budget? You forgot to carry the 1. Want to win hearts and minds in a far-away country? You might want to get the language right. Skeptics can be excessively negative, all arched eyebrows and begging to differ. But sometimes skeptics stop everyone from going off the deep end.

When someone says Big Foot or space visitors, I think misperception or hoax. But the skeptic in me has to note that strange new species are discovered every year. It was only in 2006 that Japanese scientists got the first images of a giant squid (Architeuthis) in the wild.

As for crop circles, I’m sure most are done by midnight pranksters, though I once interviewed William Levengood, a retired professor of physics at the University of Michigan. He had carefully studied samples of grain and soil from crop circles and thought something else – perhaps an ionospheric anomaly – was going on. We’ve had only a century of experience with weather balloons and rocketry. Do we know everything there is to know about the ionosphere?

As for ESP: People who claim they are clairvoyants or can bend spoons with their thought are charlatans in my opinion. But all of us have experienced coincidences too odd to explain. A person you were thinking about phones in the next second. A lost object reappears. Psychologists and physiologists think these are just mental hiccups. Perhaps. But are we certain we are always getting clean data through our senses when we observe something? Werner Heisenberg was uncertain.

Most of what people call the paranormal is probably hogwash. But the word “probably” is where the skeptic earns his or her merit badge. The scientific process is the best and most rational way humans have of trying to understand the natural world they inhabit. It requires careful analysis and study. But it also requires continued doubt.

And that’s where we have a problem in rational discourse today. Writing in a recent issue of the Chronicle of Higher Education, Carlin Romano made a distinction between today’s “science warriors” and the real “philosophers of science.” The former take an absolutist approach to science, skewering everything from the Loch Ness monster to conventional religious beliefs as ignorance. Philosophers of science, however, understand science to be a set of beliefs and knowledge that at times can be turned on its head, a recurring process that Thomas Kuhn described in his book “The Structure of Scientific Revolutions.”

That night when I stood under the stars with Maddy, my dear departed friend and mother-in-law, I saw a light moving way up in the sky. It wasn’t on the smooth trajectory of a satellite. It was an object. It was flying. I could not identify it. That’s as far as I can go. Technically, Maddy was right. It was a UFO. There was probably a good explanation. Probably.

John Yemma is the editor of The Christian Science Monitor.