What do you think is the real meaning of the often quoted line from Shakespeare "All that glisters is not gold"? The strict sense would be that glistering proves a substance to be not gold. But the real sense is that glistering does not necessarily prove a substance to be gold. In other words, the proverb should, logically speaking, be "Not all that glisters is gold".
But Shakespeare wrote in the illogical way, and this illogical construction is not now uncommon. For example, if you hear an Englishman say "All my friends do not know the Han language", you must not understand him to mean that all his friends are ignorant of Han. He may very well imply that most of his friends can speak and write it very well.
This is indeed illogical. There are Englishmen who do not use this construction and fall foul of those who do. Probably it will pass away in time, for logic has time on its side. But it is natural and idiomatic English today, and I think every learner of English should know it.
There are a number of other illogicalities in English that are quite idiomatic. Please read the first sentence of the second paragraph of this article again. Perhaps you will think that "is not now uncommon" is not so good as "is now not uncommon" would be. According to logic, indeed, "not" ought to modify "uncommon" instead of "now". But according to idiom "is not now uncommon" is more usual.
With the word "only", illogical and idiomatic constructions are also common. An Englishman may say "I only arrived a few days ago", when he means that he arrived only a few days ago.
As I have said, logic has time on its side. But how many years the English language will take to become a perfectly logical speech!
NOTES
1. Shakespeare 指William Shakespeare(1564-1616)莎士比亚，英国剧作家和诗人
2. "All that glisters is not gold" 一切闪光的东西不都是金子
3. does not necessarily 未必；不一定
4. logically speaking 按照逻辑讲
5. ignorant of the Han language 不懂汉语
6. fall foul of... 与...争吵
7. do=use this construction
8. will pass away in time 将来总须消灭
9. has time on its side 有时间为它支持；日后它必将胜利
10. But how many years the English language will take to become a perfectly logical speech! 但英语要经过多少年才能成为一种完全合于逻辑的语言！
