This spirited and challenging book presents dialogues between eminent art historians on current topics and dilemmas in the field. The essays consider world art of all periods, covering ancient Egypt, Mesopotamia, preconquest Mexico and Peru, Islam, China, Japan, Renaissance and baroque Italy, 18th- and 19th-century France, and the United States in the 20th century and today.   The authors propose new readings as they challenge traditional systems of classification; interpret monuments in terms of their interaction with their environments; redefine the Italian Renaissance in light of the new vernacular sensibility that emerged in the Trecento; view portraiture both in close detail and in social and historical perspective; and point to the need to reconcile historical coherence with complexity in museum displays.    Contributors include Svetlana Alpers, Elizabeth Hill Boone, Philippe Bordes, Betsy M. Bryan, C. Jean Campbell, Joseph Connors, Charles Dempsey, Marian H. Feldman, Finbarr Barry Flood, Hal Foster, Marc Gotlieb, Ewa Lajer-Burcharth, Michael Leja, Yukio Lippit, Joanne Pillsbury, Louise Rice, David J. Roxburgh, Jeffrey Weiss, Mariët Westermann, and Wu Hung.