When my granddaughter was little, I used to take her on a walk near our house. Crossing a footbridge over the little creek, I would tell her the story about the troll and the Billy goats. After a while, she began grasping my hand as we crossed.

One day, as we were approaching the bridge, she said, “Abba. I have been thinking about trolls.”

“Oh?” I said, surprised.

“I’ve decided that trolls might be small and not big.” Waiting a moment, she added, “and, trolls might be nice and not mean.”

I nodded, admitting this was a possibility.

“I have not even seen a troll,” she continued. “Have you?”

I admitted I had not.

“There might not even BE trolls,” she said, now exasperated, as she burst defiantly, courageously, into a trot across the bridge.

How important critical thought is.

All people are created equal. All ideas are not. Some ideas can be supported. Others cannot stand up to scrutiny. When we insist on supporting them anyway, we destroy our capacity to discern the difference between truth and error.

For example, what if I claim that the universe and its contents shrink to half their size every twenty-four hours? If you protest, I can respond that since all our means of measurement have been experiencing the same phenomenon, we naturally have failed to note the change until now.

If I am crafty, the more nonsense I throw at you, the more plausible my assertion can seem.

“Lord, have mercy–we’re all shrinking!” you may shout. “Oh, ohh—John Lennon was a prophet. He knew! ‘How I long for yesterday’ must be a coded message about regaining his lost size—the one he had yesterday!!!!!!”

It is possible, in other words, to put oneself in the frame of mind in to believe that the universe, together with its measuring devices, are constantly shrinking. If I can lead you into that frame of mind, then connect the resulting anxiety to a product or a political narrative, I can make a handsome profit or build a following.

I can sell you an app, or a hat lined with foil, or a privileged seat in one of my closed conferences at an undisclosed location.

I found the day my granddaughter dismissed the trolls a bit sad. She didn’t need to hold my hand anymore as we crossed the bridge. Oh, she wasn’t completely sure at first. For a while she kept looking under the bridge before she crossed. But she was certain enough to walk through the anxiety to the other side.

She was growing up, learning to fact-check all the nonsense the world will throw her way.

If only we all might learn that lesson.