A language is a particular kind of system for encoding and decoding information. In its most common use, the term refers to so-called "natural languages" — the forms of communication considered peculiar to humankind. In linguistics the term is extended to refer to the human cognitive facility of creating and using language. Essential to both meanings is the systematic creation and usage of systems of symbols—each symbol referring to linguistic concepts with semantic or logical or otherwise expressive meanings.
The most obvious manifestations are spoken languages such as English or Spoken Chinese. However, there are also written languages and other systems of visual symbols such as sign languages.
Although some other animals make use of quite sophisticated communicative systems, and these are sometimes casually referred to as animal language, none of these are known to make use of all of the properties that linguists use to define language in the strict sense.
When discussed more technically as a general phenomenon then, "language" always implies a particular type of human thought which can be present even when communication is not the result, and this way of thinking is also sometimes treated as indistinguishable from language itself.
In Western philosophy for example, language has long been closely associated with reason, which is also a uniquely human way of using symbols. In Ancient Greek philosophical terminology, the same word, logos, was used as a term for both language or speech and reason, and the philosopher Thomas Hobbes used the English word "speech" so that it similarly could refer to reason, as discussed below.
[edit] Properties of language
A set of commonly accepted signs (indices, icons or symbols) is only one feature of language; all languages must define (1) the structural relationships between these signs in a system of grammar, (2) the context wherein the signs are used (pragmatics) and (3) dependent on their context the content specificity, i.e. its meaning (semantics). Rules of grammar are one of the characteristics sometimes said to distinguish language from other forms of communication. They allow a finite set of signs to be manipulated to create a potentially infinite number of grammatical utterances. However, this definition is self-circular. The structural relationships make sense only within language; the structure of language exists only in language. It is impossible to have a logically correct definition of a noun or verb. And logic itself concerns itself with propositions which are closely linked with content specificity i.e. semantics.
Another property of language is that its symbols are arbitrary[1]. Any concept or grammatical rule can be mapped onto a symbol. In other words, most languages make use of sound, but the combinations of sounds used do not have any necessary and inherent meaning – they are merely an agreed-upon convention to represent a certain thing by users of that language. For instance, the sound combination nada carries the meaning of "nothing" in the Spanish language and also the meaning "thread" in the Hindi language. There is nothing about the word nada itself that forces Hindi speakers to convey the idea of "thread", or the idea of "nothing" for Spanish speakers. Other sets of sounds (for example, the English words nothing and thread) could equally be used to represent the same concepts, but all Spanish and Hindi speakers have acquired or learned to correlate their own meanings for this particular sound pattern. Indeed, for speakers of Slovene and other South Slavic languages, the sound combination carries the meaning of "hope", while in Indonesian, it means "tone".
This arbitrariness even applies to words with an onomatopoetic dimension (i.e. words that to some extent simulate the sound of the token referred to). For example, several animal names (e.g. cuckoo, whip-poor-will, katydid) are derived from sounds the respective animal makes, but these forms did not have to be chosen for these meanings. Non-onomatopoetic words can stand just as easily for the same meaning. For instance, the katydid is called a "bush cricket" in British English, a term that bears no relation to the sound the animal makes. In time, onomatopoetic words can also change in form, losing their mimetic status. Onomatopoetic words may have an inherent relation to their referent, but this meaning is not inherent, thus they do not violate arbitrariness.
[edit] Origin of language
Ancient Tamil inscription at the Brihadeeswara Temple in ThanjavurMain article: Origin of language
Even before the theory of evolution made discussion of more animal-like human ancestors commonplace, philosophical and scientific speculation casting doubt on the use of early language has been frequent throughout history. In modern Western philosophy, speculation by authors such as Thomas Hobbes and later Jean-Jacques Rousseau led to the Académie française declaring the subject off-limits.[citation needed]
The origin of language is of great interest to philosophers because language is such an essential characteristic of human life. In classical Greek philosophy such inquiry was approached by considering the nature of things, in this case human nature. Aristotle, for example, treated humans as creatures with reason and language by their intrinsic nature, related to their natural propensities to be "political," and dwell in city-state communities (Greek: poleis)[2].
Hobbes, followed by John Locke and others, claimed that language is an extension of the "speech" which humans have within themselves, which in a sense takes the classical view that reason is one of the most primary characteristics of human nature. Others have argued the opposite - that reason developed out of the need for more complex communication. Rousseau, despite writing[3] before the publication of Darwin's theory of evolution, claimed that there had once been humans who had no language or reason and who developed language first—rather than reason—the development of which he explicitly described as a mixed blessing, with many negative characteristics.
Since the arrival of Darwin, the subject has been approached more often by scientists than philosophers. For example, neurologist Terrence Deacon in his Symbolic Species has argued that reason and language "coevolved." Merlin Donald sees language as a later development building upon what he refers to as mimetic culture,[4] emphasizing that this coevolution depended upon the interactions of many individuals. He writes that:
A shared communicative culture, with sharing of mental representations to some degree, must have come first, before language, creating a social environment in which language would have been useful and adaptive.[5]
The specific causes of the natural selection that led to language are however still the subject of much speculation, but a common theme which goes right back to Aristotle is that many theories propose that the gains to be had from language and/or reason were probably mainly in the area of increasingly sophisticated social structures.
In more recent times, a theory of mirror neurons has emerged in relation to language. Ramachandran [6] has gone so far as to claim that "mirror neurons will do for psychology what DNA did for biology: they will provide a unifying framework and help explain a host of mental abilities that have hitherto remained mysterious and inaccessible to experiments". Mirror neurons are located in the human inferior frontal cortex and superior parietal lobe, and are unique in that they fire when completing an action and also when witnessing an actor performing the same action. Various studies have proposed a theory of mirror neurons related to language development [7][8][9].
[edit] Language May Have Evolved from Visual-Spatial Working Memory During the Evolution of Stone Tool Technology
Vandervert (2009a, 2009b; Vandervert, Schimpf & Liu, 2007) proposed a neuro-cognitive explanation of the evolutionary relationship between reason and language. According to this view, a new class of mental capacities evolved within human working memory which was selected in a step-by-step collaboration with evolving cognitive functions of the cerebellum. This new class of mental capacities evolved from visual-spatial working memory, which we share with animals, and came to constitute the articulatory speech loop of working memory (see working memory). Noting that the human cerebellum has experienced a fourfold increase in size in the last million years, Vandervert believes the main drivers of the evolutionary selection toward uniquely human mental and communicative capacities (of which language is only a portion) were the requirements of coordinated working memory-cerebellar control during 100’s of thousands of years of stone tool technology evolution. That is, over millennia the making of stone tools required progressively more complex blending between structured, planned intentions of the central executive of working memory and refined, repetitive composite series of perceptual/motor control by the cerebellum (see Hautzel, Mottaghy, Specht, Muller & Krause, 2009 for central executive functions of the cerebellum). The cerebellum constantly refined the processes of working memory on the one hand, and the repetitive execution of complex knapping (stone sculpting) movements on the other; thus this process formed a positive feedback loop between the two.
参考资料：http://zhidao.baidu.com/question/128136923.html?si=2