Atanu Dey writes in his next letter to Abhishek:
You are a sentient human being who is capable of using symbols.
There is one fact that distinguishes us from the rest of creation: our ability to use language. Or to put it another way, our ability to do abstract symbol manipulation. That ability, more than anything else, allows us to call ourselves members of the species homo sapiens sapiens. All our best attributes flow from that unique faculty. How did our brains diverge from the brains of our pre-human ancestors? What were the evolutionary forces which molded our neocortex? These are questions that are fascinating to explore. Even the capacity to ask these questions and answer them in some fashion requires the ability to manipulate symbols. You will notice that there is a certain circularity involved in this process: we use the faculty to explore the same faculty.
A large vocabulary is important if you want to be able to think effectively and clearly. As I noted before, education is about vocabulary (symbols) and thinking (manipulation of symbols.) The fact is that while thinking requires words as the objects upon which it operates, thinking itself creates more words. As more people think in the world, the collective vocabulary of the world goes up and this is what increases our ability to think more clearly.