Of all the mind tools we acquire in the course of furnishing our brains from the stockpiles of culture, none are more important, of course, than words — first spoken, then written. Words make us more intelligent by making cognition easier, in the same way (many times multiplied) that beacons and landmarks make navigation in the world easier for simple creatures. Navigation in the abstract multidimensional world of ideas is simply impossible without a huge stock of movable, memorable landmarks that can be shared, criticized, recorded, and looked at from different perspectives.
Daniel Dennett