1.1 What is language?

　 We use language in most of our waking life (and sometimes in dreams, too). Language is so indispensable to us that we all tend to take it for granted. Few of us ever think about what it is that allows us to talk about everything in the universe and our inner world, to do things together with others. As a learner of a foreign language, have you ever thought about the nature of the subject that you learn through painstaking effort? As a professional English teacher, have you ever pondered at the nature of the subject you teach?

　 Probing into this question, one may understand the multi-faceted nature of language. Language is many things indeed: a medium of communication, a system of code, a carrier of culture, an instrument for thinking, a glue of a community, a social institution, etc. This multi-faceted nature of language explains the fact that there is no universally accepted definition of language. Linguists must face up to this question, as language is the object of study in their research. Hundreds of definitions have been proposed in the past. We cite a few here for discussion. （注解）

Language is a system whose parts can and must be considered in their synchronic solidarity.(de Saussure, 1916)

[Languages is] a set (finite or infinite) of sentences, each finite in length and constructed out of a finite set of elements (Chomsky, 1957)

Language is a purely human and non-instinctive method of communicating ideas, emotions and desires by means of voluntarily produced symbols. (Sapir, 1921)

　 Each of these definitions pinpoints some aspects of the essence of language, but all have left out something.

　 In broad terms, linguists agree to define language as a system of arbitrary vocal symbols used for human communication (Wardhaugh 1977). This definition is based on a number of theoretical assumptions. Defined as such, language is seen as unique to human beings. In other words, it is assumed that only human beings have language. Animal communication systems (bird chips, bee dances, dog barks, and so on), are all excluded. Is this justified? Are communication systems possessed by other creatures qualitatively different from human languages?