This article deals with the relationship between language and thought, focusing on the question of whether language can be a vehicle of thought, as, for example, Peter Carruthers has claimed. We develop and examine a powerful argument—the "argument from explicitness"—against this cognitive role of language. The premises of the argument are just two: (1) the vehicle of thought has to be explicit, and (2) natural languages are not explicit. We explain what these simple premises mean and why we should believe they are true. Finally, we argue that even though the argument from explicitness shows that natural language cannot be a vehicle of thought, there is a cognitive function for language.