Several cultures have independently viewed the main function of language as the expression of thought. Ancient Indian grammarians speak of the soul apprehending things with the intellect and inspiring the mind with a desire to speak; and in the Greek intellectual tradition Aristotle declared, "Speech is the representation of the experiences of the mind- (On Interpretation). Such an attitude passed into Latin theory and thence into medieval doctrine. Medieval grammarians envisaged three stages in the speaking process: things in the world exhibit properties; these properties are understood by the mind of man; and, in the manner in which they have been understood, so they are communicated to others by the resources of language.
Rationalist writers on language in the 17th century gave essentially a similar account: speaking is expressing thoughts by signs invented for the purpose, and words of different classes (the different parts of speech) came into being to correspond to the different aspects of thinking.
Such a view of language continued to be accepted as generally adequate and gave rise to the sort of definition proposed by Henry Sweet and quoted above. The main objection to it is that it either gives so wide an interpretation to thought as virtually to empty the word of any specific content or gives such a narrow interpretation of language as to exclude a great deal of normal usage. A recognition of the part played by speaking and writing in social cooperation in everyday life has highlighted the many and varied functions of language in all cultures, apart from the functions strictly involved in the communication of thought, which had been the main focus of attention for those who approached language from the standpoint of the philosopher. To allow for the full range of language used by speakers, more comprehensive definitions of language have been proposed in recent years on the lines of the second one quoted above (i.