Being a witness is most often accidental; being an observant witness is an effort. Irving Sandler had no peers in the later 20th century as a witness to the changes in art and the lives of artists. His assiduous note-taking and powers of synthesis are legendary, rightfully so. History itself is an accretion, and made richer in its retelling by participants. For more than 60 years, Irving was near or at the center of the New York scene. Part of his charm was in his assumption that you were in the epicenter as well, hence the reliable opening, “Tell me what is happening”—often in my case embellished with the additional “young fellow.” If his curiosity ever flagged, I didn’t see it. His insatiable taste for the new coupled with a manifest enthusiasm for art and artists, made Irving Sandler a special, even unique figure. A creature of mid-century Abstract Expressionist aesthetics, he kept looking until the end. Modern art in America has lost its most senior, accurate, and industrious historian. We have lost a generous friend.