Koľko rečí vieš, toľkokrát si človekom. (Slovak)
Сколько языков ты знаешь – столько раз ты человек. (Russian)
This thought occurs as a proverb in several Slavic and even other languages. It means “As many languages as you know, so many separate individuals you are worth.” It’s not quite easy to translate, but — in my opinion — it’s generally true.
Here is an interesting article on Multiligualism.