Collectors, it sometimes seems, are a necessary evil. Artists create, and we art writers explain the significance of what they make. But collectors, who usually are privileged people, mostly only pick up the check. Too often they treat art as a form of speculation, and so are ready to resell when its value increases. And many of them are not shy about hustling for tips. As a dealer explained to me over dinner, after the newly rich purchase their houses and yacht, they come to his gallery to get their art. Well, they have to do something with their money. When magazines like Art News devote attention to collectors, they focus excessive attention on the unavoidable relationship between the art market and the superrich. Myself, sometimes when I read lavishly illustrated accounts about the hundred most important collectors, I wish that state socialism had triumphed. The Cone sisters and Isabella Stewart Gardner were collectors who came from a different world. Claribel and Etta Cone, daughters of a German immigrant who made his fortune in North Carolina textiles, were comfortable enough to travel and not to need to marry. As visitors to the Baltimore Museum of Art can see, they collected...