"It won't do to say that the reader is too dumb or too lazy to keep pace with the train of thought."

It won't do : a particular person's behavior is unsatisfactory and cannot be allowed to continue.

1. = bewilder / confuse completely 使困惑

you are? mystified by something = you find it impossible to explain or understand

2. =derogatory / obfuscate 將……神秘化

With each rewrite I try to make what I have written tighter, stronger and more precise, eliminating every element that's not doing useful work.

Clutter is the disease of American writing. We are a society strangling in unnecessary words, circular constructions, pompous frills and meaningless jargon.

上面兩個句子說的是簡潔精煉語言和冗長的語言。學(xué)習(xí)其表達(dá)。