Theories

A theory is a set of expressions in a formalism which describe (are interpreted in terms of) a model of the perceived world. The model with the associated interpratation function provides a denotational (declarative) semantics for the theory.

Abstract theory:

An abstract theory describes (is interpreted in terms of) an abstract model.

Empirical theory:

An empirical theory describes (interpreted in terms of) an empirical model.

Operational theory:

An operational theory describes (is interpreted in terms of) an operational model, i.e. a computer programme.

Special theory:

A special theory describes (is interpreted in terms of) a specific domain with specific methods, for instance a specific grammar or lexicon or phonological description.

General theory:

A general theory describes (is interpreted in terms of) a class of special theories, and therefore generalises over these, for instance universal grammar or the theory of the lexicon.