  With the two basic categories of sentence and name, every category and expression, no matter how complex, will have a categorial index beginning either with ‘S’, so ultimately leading to the formation of a sentence, or ‘N’, so ultimately leading to the formation of a name. Following a useful terminological suggestion of Eugene Luschei, we may call the former propositive categories and expressions, the latter nominative categories and expressions (Luschei 1962, 169).