The less we know about a subject, the less we think there is to know about it.
That’s why the boss who knows nothing about your specialty will demand impossible time frames on your projects, unless someone speaks up to tell him otherwise.
It’s also why casual, amateur photographers can’t see — literally cannot see — the difference between their badly-done snapshots and a well balanced, properly focused and composed work of photographic art.
And especially, that is why people who have never had serious defensive handgun training think there’s nothing to learn and no reason to invest in it.
The opposite is also true. After 60 years of gun ownership and 30 years of teaching, there’s so much more I don’t know than I have ever known about before.