A former customer of mine is fond of the expression, "A little knowledge is a dangerous thing"

I thought I understood it, it made sense, but as I'm getting older I am realising that those of us who sees and knows the dumb shit others around us do, are at danger of being locked away for murder

@GNious

A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There shallow draughts intoxicate the brain,
And drinking largely sobers us again
-Alexander Pope

It means to learn deeply or not at all. Many people have a surface level understanding of complex topics and think they're experts. The author is warning the reader against becoming like that.

Or to put it a similar way, never stop learning.