 The historical introductory sections have aimed to show the intellectual centrality, varying formulations, and significance of the concept of unity. The rest of the entry presents a variety of modern themes and views. It will be helpful to introduce a number of broad categories and distinctions that can sort out different kinds of accounts and track some relations between them as well as additional significant philosophical issues. (The categories are not mutually exclusive, and they sometimes partly overlap; therefore; while they help label and characterize different positions, they cannot provide a simple, easy and neatly ordered conceptual map.)