rtet, Essays in the Study of Sienese Painting was published in 1918. An affair in Paris with Baroness Gabrielle La Caze, a French art collector, ensured. The following year, Berenson hired Elisabetta "Nicky" Mariano (1887-1968) to be his librarian and secretary. In 1925 the young Japanese scholar of Botticelli, YukioYashiro began to assist Berenson with a new edition of Drawings of the Florentine Painters. Berenson, apparently somewhat prejudiced against Japanese fell out with Yashiro, replacing Yashiro with a young Renaissance scholar from Oxford, Kenneth Clark, introduced Berenson by then Keeper of the Art Department of the Ashmolean Museum, Oxford, Charles F. Bell. Clark, still a student, assisted Berenson in the revision the Florentine drawings book for over two years. Berenson issued the final of his four major publications, Studies in Medieval Painting, and a combined volume of his regional Renaissance art books, Italian Painters of the Renaissance, both in 1930. He severed his ties with Duveen permanently in 1937. The art historian Fern Rusk Shapley assisted him at I Tatti with the second edition of his Drawings of the Florentine Painters, published with her own funds in 1938. As his wife's health declined, Mariano, became Berenson's lover as well. During World War II, he found himself a virtual prisoner in I Tatti, despised as an American by the Mussolini government, but admired by the locals and protected. Berenson and Mariano hid at a friend's house, fearful his Jewish heritage would make him a target. Mary Berenson died away from him at I Tatti in 1944. His war diary was published in 1952 as Rumour and Reflection, 1941-1944 and the notes on his reading for those years of enforced solitude as A Year's One Year's Reading for Fun, 1942 (1960). In 1948 Berenson wrote Aesthetics and History in the Visual Arts which expanded his concepts of "ideated sensations" and the notion of life-enhancing qualities of art. He continued to consult for the dealer Georges Wildenstein. His postwar writing included articles to the Italian newspaper Corriere della Sera. Berenson's final books included Alberto Sani (1950), Caravaggio (1953), and Piero della Francesca in 1954. Ever the conservative, Berenson disapproved of modern art, viewing it as a decline of form. His 1954 The Arch of Constantine, or, The Decline of Form took the same approach to the famous late classical monument. He died at Villa I Tatti in 1959 and is interred with Mary at a chapel on the grounds of I Tatti. The actress Marisa Berenson (b. 1946) is distantly related to Berenson (the daughter of his second cousin, Robert). His brother-in-law was the philosopher Bertrand Russell (1872-1970).
Berenson was the single-most influential art historian in the United States for most of the twentieth century. His writings were so famous that his four major titles, Venetian Painting in America, The Study and Criticism of Italian Art, Essays in the Study of Sienese Painting, and Studies in Medieval Painting were referred to as the "four gospels" by many English-speaking art historians. His connoisseurship-approach to art history clarified and solidly attributed much of Italian Renaissance art history, founded on the principles beginning with Karl Friedrich Rumohr through Giovanni Cavalcaselle and ultimately to Morelli. Berenson's method was most clearly stated in his 1902 essay (though written in the 1890's), Rudiments of Connoisseurship. As an historian dedicated to the object (as opposed to documentary art history, iconography, social art history, etc.), he centered the emerging discipline. Berenson's approach focused on determining the authenticity of art works rather than constructing histories in which art was created. His thrust proved particularly useful to art dealers and collectors, with whom Berenson has been criticized for having too close a relationship. Berenson's major books are essentially lists of authenticated paintings by Berenson with introductory essays. He never altered the text in the numerous editions of his books, confident his analysis was comprehensi