Before revision: 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).
After revision: In his seminal work Aspects of the Theory of Logic (1965), Noam Chomsky introduces a hierarchy of Levels of Adequacy for evaluating grammars (theories of specific languages) and metagrammars (theories of grammars).