Language is the unlimited creation of shared sense. Unlimited here means that everything that can be thought and communicated can be expressed by language. This property of language is its effability (Katz 1972: 18-23; also called productivity, Hockett 1963), the highest possible expressive power of a semiotic system.

Human language differs in this from animal communication. Animal communication is situation-bound; i.e. animals communicate ideas related to the current situation of the interlocutors. This is the speech situation in the first place, but may also be a situation in the wider environment that is currently of relevance. Human language is not restricted in this way; it is not bound up with the world surrounding us. It does not represent “reality”, but our thought, which may or may not be a representation of “reality”, as visualized in the following diagram:

language thought reality
utterance represents consciousness represents sometimes world
referential expression referent denotatum
linguistic expression mental representation physical object

This includes the option to lie. The possibility to lie, taken as a feature of a communication system, is called prevarication (Hockett 1963). Again, some animals are able to deceive their mates about an aspect of the current situation; but this is where prevarication ends in animal communication.

Effability is a defining feature of language. As a consequence, a semiotic system that lacks it – e.g. the bees' “language” – is not a language. It may be empirically ascertained that every natural human language so far discovered has effability. Non-human primate communication lacks it. Since human language developed from primate communication, it acquired effability during its evolution. In principle, the point in time where this happened is the origin of human language. From a methodological point of view, this is, however, not helpful since we cannot empirically ascertain whether some prehistorical semiotic system possessed effability.

The definition of effability relies on the condition that everything that can be thought and communicated can be expressed. With this, the concept is covertly anthropocentric (i.e. relative to our species). It is quite imaginable that an extraterrestrial intelligence finds human language lacking in effability. However, even if we accept this, language as delimited by the condition of effability may, in turn, be used as a definitory feature of Homo sapiens: he1 is the only creature that possesses language. Such a move is fraught with theoretical and methodological problems discussed on another page.


1 In this text, the pronoun he implies nothing for the sex of its referent.


Katz, Jerrold J. 1972, Semantic theory. New York etc.: Harper & Row (Studies in language).