Bernard Berenson (1865-1959) was an American connoisseur of Lithuanian Jewish extraction who was a hugely significant figure in the evolution of the commercial art world from the late 1880s to the 1940s. This book examines his conception of connoisseurship and its impact through his famous protégés, who included Geoffrey Scott, Meyer Shapiro, John Walker and especially art historian Kenneth Clark, of Civilisation fame. This is framed through a biographical account of Berenson’s complex and duplicitous character, together with a description of his important methods for determining authorship and assigning value to Renaissance artworks. In terms of the assignation of authorship and the determination of value, Berenson remains a seminal if contradictory figure in the history of the art market, for whom the artwork was subject to a series of negotiations and the act of connoisseurship was both an aesthetic pursuit and a ‘scientific process’. Berenson’s commercial dealings ran counter to his own assertion that the connoisseur needed to be ‘disinterested’ in their consideration of art and engaged in an other-worldly ‘art in life’. The book examines Berenson’s complex and lucrative dealings with the industrialists of the American Gilded Age, including Isabella Stewart Gardner. These transactions were enmeshed in issues of authenticity and forgery, as well as inflated estimates and unscrupulous skimming from both clients and business partners, including the notorious dealer Joseph Duveen.These negotiations afforded him such celebrity and financial gain that 'everyone', as Marcel Proust once quipped, 'wanted to know about Berenson'. In this way, Berenson is not only an historic figure, but also a precursor to those sometimes slippery intermediaries who appear throughout the history of contemporary art.