Abstract
This chapter discusses that some languages have a much simpler grammatical apparatus than the familiar Indo-European languages do, morphologically, syntactically, and semantically. It presents a broad overview of the issues that are relevant to a theory of lexical categories from a more standard generative perspective. It discusses the pros and cons of dividing up the four lexical categories into natural classes using two distinctive features, and reviews how the intertwined theories of functional categories, selection, and head movement can explain familiar differences in how nouns and verbs are inflected. The chapter also deals with the question as to whether different languages have diverse category systems, without having a clear theory of the distinctions among the lexical category. The chapter postulates that it is necessary to have theories of the syntactic categories that aspire to this kind of explanatory depth in order to finally resolve whether languages differ significantly in their syntactic category systems or not.