We can wonder about what others are thinking or feeling without ever hearing them say a word. 

My toddler holds an empty ice cream cone, looking despondently at a melting ball of goo on the ground. It is obvious that she is sad she lost her treat. An orangutan brushes his head with a leaf, then hands the leaf to a human caregiver. For anyone familiar with the orangutan sanctuary in Indonesian Borneo, it is clear the orangutan wants his head cleaned. An extraterrestrial spaceship is observed approaching Earth. Humanity hopes their intentions are peaceful.  

The ideas we have about young children's, animals' or aliens’ feelings and intentions suggest that it is possible to be a thinker without being a speaker. But some philosophers have denied it, arguing that only language users can believe anything. Understanding this view requires a little unpacking about what language and belief are.