Drawing on evidence from neurobiology, cognitive science and corpus linguistics, MIT researchers make the case that language is a tool for communication, not for thought.
I think transforming "it's possible to think without language" into "language is not a tool for thought" is an overreach. Definitely a lot of our internal voice is post-thought, but crystalizing those thoughts into words can provide footholds for further thought. Some would argue it's not possible to think through a complex issue without writing: