Posted by: dtyler27106
Well, -blam!-. I was gonna say language.
EDIT: You forgot one of the most important reasons, OP. We use it to think.
I thought about it but decided not to because even people, such as Helen Keller, didn't have any form of language at first but still were capable of thinking. Language may provide us with a more complex way of thinking than pure raw emotions but it isn't quite necessary.