Spoken language, is language produced by articulate sounds, as opposed to written language. Many languages have no written form, and so are only spoken. Oral language or vocal language is language produced with the vocal tract, as opposed to sign language, which is produced with the hands and face. The term “spoken language” is sometimes used to mean only vocal languages, especially by linguists, making all three terms synonyms by excluding sign languages. Others refer to sign language as “spoken”, especially in contrast to written transcriptions of signs. In spoken language, much of the meaning is determined by the context. This contrasts with written language, where more of the meaning is provided directly by the text. In spoken language the truth of a proposition is determined by common-sense reference to experience, whereas in written language a greater emphasis is placed on logical and coherent argument; similarly, spoken language tends to convey subjective information, including the relationship between the speaker and the audience, whereas written language tends to convey objective information. The relationship between spoken language and written language is complex. Within the field of linguistics the current consensus is that speech is an innate human capability while written language is a cultural invention. However some linguists, such as those of the Prague school, argue that written and spoken language possess distinct qualities which would argue against written language being dependent on spoken language for its existence. Both vocal and sign languages are composed of words. In vocal languages, words are made up from a limited set of vowels and consonants, and often tone; in sign languages, words are made up from a limited set of shapes, orientations, locations, and movements of the hands, and often facial expressions; in both cases, these building blocks are called phonemes. In both vocal and sign languages, words are grammatically and prosodically linked into phrases, clauses, and larger units of discourse. Hearing children acquire as their first language whichever language is used around them, whether vocal or (if they are sighted) sign. Deaf children will do the same with sign language, if one is used around them; vocal language must be consciously taught to them, in the same way as written language must be taught to hearing children. (See oralism.)