All of our thought processes are conducted in language, so really our entire existence or essence or soul, however we phrase it, is inextricably bound to and with the languages we speak. Try to think without language for instance. However, we see that the language is in essence superficial, since many languages exist. To understand the true roots of our thought processes, the real nature of the human soul, a knowledge of several languages may be necessary.

Most people in the world are multilingual, and everybody could be; no one is rigorously excluded from another’s language community except through lack of time and effort. Different languages protect and nourish the growth of different cultures, where different pathways of human knowledge can be discovered. They certainly make life richer for those who know more than one of them.

~ Nicholas Ostler, Empires of the Word

Die Grenzen meiner Sprache bedeuten die Grenzen meiner Welt.
The limits of my language are the limits of my universe.

~ Ludwig Wittgenstein

I’m hesitant to disagree with Wittgenstein, but the limits of my thoughts (or my universe) far exceed that of my language. But I still love this sentiment, and it’s definitely true that learning a language will expand your universe, opening up new worlds of literature and culture.

Kolik jazyků znáš, tolikrát jsi člověkem.
The more languages you know, the more you are human.

~ Tomáš Garrigue Masaryk