How many old people would claim that they only thought they knew everything when they were young? And it’s what they learned after that time?

that counts?
Answers

Cogito

Every one of us - if they're reasonably intelligent and honest.

ProfGene.Togolot

Anyone who is honest would admit that.

Fred

There is an old saying for young people to get out there and get a job while they still know everything. Yes many teenagers think they know all there is to know but fund as adults how little they really do know. I think most of us have been through this.

Rebecca Angela

I wouldn't say 'OLD', I would say 'ELDERLY'. My father is 75 and he doesn't consider himself old and he admits there are still a lot of things to learn about life itself. Yes, he did think he knew everything when he was young and now he knows a lot more. He was a Karate instructor, a photographer, a baseball coach, went regular winter mountaineering just to name a few. He was also a trucker and taxi driver and now he is a self-published author on 'Zon'.

Sir Caustic

Three?

Ludwig

All of them. But they are all senile so don't pay any attention.