http://www.taoteching.org/

"My words are easy to understand
And my actions are easy to perform
Yet no other can understand or perform them.
My words have meaning; my actions have reason;
Yet these cannot be known and I cannot be known."

"Understanding" is a pretty complicated process. Hofstadter had a pretty good definition: Understanding is a homomorphy between two symbolic systems.

You can write a few 100s pages just on this topic.

1. You can not understand your opponent if you both have different sets of symbols. Unfortunately, nobody has exactly the same set, that's why people keep bitching about labels and definitions all the time.

2. If you call somebody "redneck", or "black", or "liberal", or any other label, many people attack you for being a bigot. Unfortunately, our brain has to assign labels to everything in order to even start thinking. You can argue about definitions for those labels, you can modify your labels with adjectives, you can create new labels, but using labels is unavoidable.

"Who understands the Way seems foolish;
Great truth seems contradictory;
Great cleverness seems stupid;"

Few logical conclusions:
If you understand the Way, you seem foolish -> If you don't seem foolish, you don't understand the Way -> If you seem foolish, you may understand the Way (or you may simply be an idiot)

"Honest people use no rhetoric;
Rhetoric is not honesty.
Enlightened people are not cultured;
Culture is not enlightenment."

Yes, and education is not wisdom.

"Without taking a step outdoors
You know the whole world;
Without taking a peep out the window
You know the colour of the sky.
The more you experience,
The less you know."

Anecdot: There is a difference between a Russian (East-European) and an American specialist: Russian knows nothing about everything, American knows everything about nothing.

"Who understands does not preach;
Who preaches does not understand."

Problem with establishing homomorphy between two symbolic systems again. When you try to explain anything complicated, you have to create easily understandable labels and to simplify relationships between them, otherwise your listeners will never get it. On the other hand, it is so much easier preaching to the choir, when everybody shares the same symbolic system already.

From another translation:
"Emptiness is the mother of 10,000 things;
Naming is the father of 10,000 things."

That's about labeling again.

The Way is emptiness, it is whole, it is formless, it is not realized yet, it is female waiting for male.

And then you start to divide the whole, to label individual pieces, to give them names, to establish simplified behaviors and relationships between them. Male is rude, male is primitive, male is force, male is action. And of course the more detailed symbolic system you build, the further you are from the whole.