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.    

My daughter doesn’t yet use language. The orangutan, like all nonhuman animals, doesn’t have a natural language system. The aliens might not have anything like a human language; suppose they share a joint mind and communicate with one another the way subsystems of our body do. These beings can communicate, but they don’t use language—that human method of communication that has grammatical structure allowing us to create sentences, logical structure allowing us to make inferences from sets of sentences to new sentences, and which permits these sentences to have truth value.

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"Language is powerful, but not so powerful that it creates thoughts out of nothing"

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Beliefs are often described as mental representations that have propositional structure, which means they can be characterised in terms of sentences. They permit rational inference such that we can use sets of beliefs about the world to infer new things about the world, and have truth value such that our beliefs are either true or not.

Given the parallel structure between belief and language, perhaps it shouldn’t be surprising that some people think that it is impossible to have belief without language. Language and belief both appear to have sentential structure that allows us to think things like: All dogs are mammals, Fido is a dog, and from those two thoughts conclude that Fido is a mammal. From these sorts of observations, we develop hypotheses. Maybe we think in language! Maybe language is required to have a thought at all. Maybe it is linguistic structure that allows us to solve problems and construct generalisations. After all, language is like magic, permitting the creation of an infinite number of new thoughts with its finite set of tools.  

It’s not a bad hypothesis, but it doesn’t hold up to scrutiny. Language is powerful, but not so powerful that it creates thoughts out of nothing. Language can be used to create new concepts which allow us to think new thoughts, so with language we can create beliefs that we never had before. An alternative hypothesis is that without something to think about in the first place, there would be nothing to talk about. Thoughts drive language. 

According to the alternative hypothesis, language is a tool for communicating thoughts. If the function of language is to communicate what we think, we have another explanation for the parallel structure between belief and language:  belief is required for language, but language is not required for belief. 

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"Belief is required for language, but language is not required for belief"

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