Unless I've already stated otherwise, I think chapter 71 of the Tao Teh Ching is my favorite chapter. It's a wise admonition that I'm sure most of us who are teachers have forgotten more than once. There's nothing more apt to make you think you know everything than a class of students who know very little and don't care to learn much more.
Chapter 71 is a short but important chapter in the Tao. De Grazia translates it:
To know that you do not know is the best.
To pretend to know when you do not is a disease.
Only when one recognizes this disease as a disease can one be free from the disease.
The sage is free from the disease.
Because he recognizes this disease to be disease, he is free from it.
while Van Over translates it:
The Disease of Knowing
To know and yet (think) we do not know is the highest attainment; not to know (and yet think) we do know is a disease.
It is simply by being pained at (the thought of) having this disease that we are preserved from it. The sage has not the disease. He knows the pain that would be inseparable from it, and therefore he does not have it.
This recognition of fallibility is probably one of the wise man's greatest strengths in finding truth, though it is certainly less valuable when it comes to convincing others you have found that truth.
Strangely this passage reminds me of a line from Yeats' "The Second Coming:" "The best lack all convictions, while the worst/ Are full of passionate intensity."
There seems to be a fine line between "knowing that you do not know" and lacking conviction. For instance, I long ago began to avoid religious arguments with "true believers" because I was far too willing to admit possibilities while they were absolutely sure that they knew the "truth," a truth I found ultimately unknowable. I'm sure these "true believers" took this to mean that I agreed with their position, or, at the very least, that I could do nothing to refute their "truths." All it really meant was that I had cut myself off from any truth that they might have known.
On the political level, I'll admit I do not have answers for most of the world's problems, but I'm absolutely convinced that those in power who think they know all the answers and who are sure they are good and others "evil" can only make matters worse. The question remains, how do you convince those who are looking for simple answers that there are none and that to accept simple answers is to doom yourself to one more turn of the wheel?