This work describes the establishment of empirically-testable models in functionalist phonological description and the use of Cartesian tables in phonological mode. A clear distinction is drawn between theoretical (meta-) statements and descriptive statements (that is, those which may be confronted with phonetic phenomena subjected to appropriate testing). A new type of Cartesian table is introduced, first in the description of combinations of distinctive features, and then of combinations of phonemes. Further models of well-formed complexes of distinctive features and phonemes are established on the basis of the tables. Examples of the application of the method are drawn from a number of languages, particularly English, French, and Russian.