It is not that you must have a PhD to push the boundaries of knowledge, it is that you must push the boundaries of knowledge to get a PhD, by definition. Nobody claimed otherwise here.

You are right about that - I merely wanted to highlight that there are always other avenues of enlarging the sum of human knowledge. Investing your mental resources into a PhD is only one path a person can choose in order to strive reaching that goal.

That is what I love about HN - Comments are dissected in a constructive manner.

The nice part about the Ph.D route is that you have guides to take you to the boundary and point it out to you.

Plenty of people think they're at the boundary and pushing but are actually stuck at a (close in) local maxima of crackpottery.

The real geniuses never even see a boundary. They just do their thing and let everyone else put labels on it later.

"Plenty of people think they're at the boundary and pushing but are actually stuck at a (close in) local maxima of crackpottery."

That is true in many cases in Academia as well.