In his paper, Ray Jackendoff puts forward a compelling case as to why thought and language are not the same thing. Indeed, thought takes place in the unconscious mind as a matter of processing whilst language is experienced consciously. The brain possesses ‘modules’ that effectively translate from thought to language and vice versa. The second half of the paper explores what language adds given that so much of the hard work seems to be done by (unconscious) thought. Most obviously, language enables us to communicate with our fellow beings. More subtly, language is the means by which attention can be directed at certain thoughts, thereby prioritising them.
Link to paper: https://www.researchgate.net/publication/233656485_How_Language_Helps_Us_Think