It's a cliché now to say that we don't know how to build something anymore, when illiterate peasants could do it 500+ years ago.

But we really don't know how to replicate the rich blues of the stained glass windows of Chartres Cathedral. We can mimic, but we can't reproduce the exact same vibrancy. The process is a lost medieval secret.

It really is possible for an entire civilization to forget something. The same fragility of knowledge transfer exists today, despite our arrogance.

I only hope we aren't foolish enough to lose modern dentistry.