My grandmother is 79. On Friday she took apart my own argument, and she was right.

My grandmother is 79. On Friday she took apart my own argument, and she was right.

I had written that the man at the cinema box office never asked her age. He just looked and nodded. I called that restraint.

"He didn't nod because he was careful," she said. "He nodded because he knew me."

Small town near Frankfurt, under 10,000 people. Everybody knew everybody. The village was the database.

Then she added the part that actually hurt:

"Back then a 12-year-old looked 12. They don't anymore."

She's right about that too. The old check was a pair of eyes. Free, instant, private — and now broken. Makeup, height, a filter on the phone. Looking does not work.

So we replaced the eyes. With the one thing every person now carries: a document.

Not because it's the right answer. Because it's the available one.

Here's my question for the week:

What would you build if nobody had a document to show?