How to compare major word-classes across the world's languages

In this paper, I argue that major word-classes, such as nouns, verbs and adjectives, cannot be compared across languages by asking questions such as "Does language X have a noun-verb distinction?". Such questions are routinely asked by linguists (functionalists and generativists alike), but these are the wrong questions (cf. Croft 2000), because they make presuppositions which are not valid.