I think it depends what you mean by language. There is a kind of symbolic logic that happens in the brain, and as a programmer I might liken it to a programming language, but the biological term is defined differently. Language, as far as it is unique to humans, is the serialisation of those internal logical structures in the same way text file is the serialisation of the logical objects within a programming language. What throws most people here is that the internal structures can develop in response to language and mirror it in some ways. As a concrete example, there is certainly a part of my brain that has developed to process algebraic equations. I can clearly see this as distinct from the part that would serialise them and allow me to write out the equation stored internally. In that way, the language of mathematics has precipitated the creation of an internal pattern of thought which one could easily confuse for its serialisation. It seems reasonable to assume that natural language could have similar interactions with the logical parts of the mind. Constructs such as “if/then” and “before/after” may be acquired through language, but exist separate from it.

Language is, therefore, instrumental to human thought as distinct from animal thought because it allows us to more easily acquire and develop new patterns of thinking.