In his seminal 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). Motivation 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. " Chomsky, 1957, p. 106. The levels Observational Adequacy The theory achieves an exhaustive and discrete enumeration of the data points. There is a pigeonhole for each observation. Descriptive Adequacy The theory formally specifies rules accounting for all observed arrangements of the data. The rules produce all and only the well-formed constructs (relations) of the protocol space. " ...the grammar gives a correct account of the linguistic intuition of the native speaker, and specifies the observed data (in particular) in terms of significant generalizations that express underlying regularities in the language. " Chomsky 1964, p. 63 Explanatory Adequacy The theory provides a principled choice between competing descriptions. It deals with the uttermost underlying structure. It has predictive power. " A linguistic theory that aims for explanatory adequacy is concerned with the internal structure of the device [i.e. grammar]; that is, it aims to provide a principled basis, independent of any particular language, for the selection of the descriptively adequate grammar of each language. " Chomsky 1964, p. 63.
In his seminal 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). Motivation 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. Chomsky, 1957, p. 106. The levels Observational adequacy The theory achieves an exhaustive and discrete enumeration of the data points. There is a pigeonhole for each observation. Descriptive adequacy The theory formally specifies rules accounting for all observed arrangements of the data. The rules produce all and only the well-formed constructs (relations) of the protocol space. ...the grammar gives a correct account of the linguistic intuition of the native speaker, and specifies the observed data (in particular) in terms of significant generalizations that express underlying regularities in the language. Chomsky 1964, p. 63 Explanatory adequacy The theory provides a principled choice between competing descriptions. It deals with the uttermost underlying structure. It has predictive power. A linguistic theory that aims for explanatory adequacy is concerned with the internal structure of the device [i.e. grammar]; that is, it aims to provide a principled basis, independent of any particular language, for the selection of the descriptively adequate grammar of each language. Chomsky 1964, p. 63.
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