There is a fundamental difference between phonologic features on the one hand, for instance [α sonorant], [α tense], [α low], [α back], and on the other hand morphologic-syntactic features such as for example [α female], [α plural], [α nominal], [α preterit], [α oblique], or semantic features such as for example [α utterance], [α speaker], [α abstract], [α human]:　 At least some of the first reflect phonetic facts, while for the latter there is no such physical basis. Phonetic-phonologic features are to some extent dependent on the physical properties of homo sapiens, while morphologic / syntactic and semantic features do not depend on the physical characteristics but in general on the cognitive faculty of homo sapiens. Morphologic, syntactic and semantic categories reflect cognitive phenomena of a special kind: They are part of the organization of the cognitive network, and as such they are organized according to principles of the cognitive competence in general. It follows from this that marking conventions and natural classes in phonologic theory are also object to different empirical evidence than marking conventions and natural classes in morphologic and syntactic theory.