He who does not know foreign languages does not know anything about his own. ~Johann Wolfgang von Goethe, Kunst and Alterthum
I agree with this statement completely. It does take a foreign language to understand and appreciate one own.
We are influenced with the way we think, therefore the structure of the language is important, words are important, idiomatic expressions are important - language is very much a part of culture.
Our language is part of our make up, we need words to be connected with our own minds and relate to others.
It does not matter how much I will say on the subject, only people who have fluency in another language will understand what I mean.
I don't mean to offend, but there are a lot of cases when people say "I speak such and such language", when in reality the knowledge is so limited...
To say "My name is such and such" and "The weather is nice" is not knowing the language.