Little do we reliably know about the Mott transition, and we are far from a complete understanding of the metal --insulator transition due to electr- electron interactions. Mott summarized his basic ideas on the subject in his wonderful book Metal--Insulator nansitions that first appeared in 1974 11. 1). In his view, a Motk insulator displays a gap for charge-carrying excitations due to electron cowelations, whose importance is expressed by the presence of local magnetic moments regardless of w ...