LOGIC AND USAGE
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 Chinese”,you must not understand him to mean that all his friends are ignorant of Chinese. He may really imply that most of his friends can speak and write Chinese 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 student 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 better.
With the word “only”,illogical yet 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!