What is the nature of a conceptual scheme? Are there alternative conceptual schemes? If so, are some more justifiable or correct than others? The later Wittgenstein already addresses these fundamental philosophical questions under the general rubric of "grammar" and the question of its "arbitrariness"—and does so with great subtlety. This book explores Wittgenstein's views on these questions. Part I interprets his conception of grammar as a generalized (and otherwise modified) version of Kant's transcendental idealist solution to a puzzle about necessity. It also seeks to reconcile Wittgenstein's seemingly inconsistent answers to the question of whether or not grammar is arbitrary by showing that he believed grammar to be arbitrary in one sense and non-arbitrary in another. Part II focuses on an especially central and contested feature of Wittgenstein's a thesis of the diversity of grammars. The author discusses this thesis in connection with the nature of formal logic, the limits of language, and the conditions of semantic understanding or access. Strongly argued and cleary written, this book will appeal not only to philosophers but also to students of the human sciences, for whom Wittgenstein's work holds great relevance.