Levels of adequacy

In his work Aspects of the Theory of Syntax (1965), Noam Chomsky introduces a hierarchy of levels of adequacy for evaluating grammars (theories of specific languages) and metagrammars (theories of grammars). These levels constitute a taxonomy of theories (a grammar of a natural language being an example of such a theory) according to validation. This taxonomy might be extended to scientific theories in general, and from there even stretched into the field of the aesthetics of art. This present article's use of the phrase as a terminus technicus should not be confused with its everyday language uses.

The "potency" criterion alluded to in the preceding section is somewhat ill defined, but may include "exhaustiveness", "effectiveness', and an affective component as well. (Arguably, the taxonomy is also motivated by considerations of "elegance". This should not be confused with the application of the taxonomy in the field of aesthetics). As a metatheory, or "theory of theories", it becomes a concept of epistemology in the philosophy of science, rather than a mere tool or methodology of scientific linguistics. As Chomsky put it in an earlier work:
The theory of linguistic structure must be distinguished clearly from a manual of helpful procedures for the discovery of grammars.

It is suggested that the system of levels proposed by Chomsky in Aspects of the Theory of Syntax has its antecedents in the works of Descartes, Kant, Carnap, Quine, and others. Certainly the criterion of adequacy found in rationalism, specifically, rational empiricism, bear some resemblance to Chomsky's formulation. Since one of the key issues which Chomsky treats in Aspects is a supposition of a congenital endowment of the language faculty in humans, the topic ramifies into questions of innateness and a priori knowledge, since it is by reference to those questions that the third level of adequacy is to be sought.

This concept should not be confused with the "causal adequacy principle," which refers to Descartes' version of the ontological argument for the existence of God in his Meditations on First Philosophy.