Knowledge is power, whether in warfare or in the art market, which greatly resembles the former in its mix of calculation and unpredictable events. Wherever knowledge is applicable in the multiple areas conventionally lumped together under the single denomination art market, it is fairly easy to determine who wields power.

Ironically, this is not the case in contemporary art, the category that outweighs all others financially. The reason is that it is the only category in which there is no need for preliminary knowledge. Contemporary art is, by definition, of the moment, although the term does not strictly refer to works created within our lifetime. Rather, by an unwritten convention thrust upon us by the auction houses and the art trade, it covers anything produced during the past five decades or so. That very convention sums up the essence of contemporary art as officially defined: Contemporary art is what you say it is. Or, more precisely, it is what those in control of the most efficient propaganda machinery put under that rubric. There is no obvious reason for characterizing as a work of art a dead beast in a glass tank filled with formaldehyde (courtesy of Damien Hirst) or crumpled canvases coated 50 years ago in white kaolin by Manzoni. The power to establish such objects as art derives from the power of mass persuasion. Its vehicles are the media and the galleries that launch the product and then sell it, literally and metaphorically, to the movers and shakers of society. In other words, power in the contemporary-art market lies with those who know how to steer trendsetters. A handful of dealers worldwide, with natural allies in publicity-hungry museums and in auction house departments requiring material to sell, deploy it with brio. Their power, however, is as precarious as it is huge—like anything that rides on the strength of discourse, also known as hot air.

In all other areas of the market, however, knowledge is a must. The situation varies depending on the availability and soundness of information and the ease of acquiring visual expertise, which together make up connoisseurship. Those who attain the highest degree of connoisseurship and combine it with strategy run the show.

In Impressionism and modern masters, the second most important category in financial terms, knowledge confers only partial control. Connoisseurs have no power to speak of in the
top echelons of the Impressionist market because so few masterpieces remain available. Prices therefore defy prediction: Some works exceed estimates by a factor of four, while others crash unsold. When expertise no longer helps to assess potential value, no one is in control.

Regarding early 20th-century masters, an area in which supply has not yet dried up, the situation is different: The oeuvre of each artist represents a category unto itself. Take early figural Picassos predating World War 1. These tend to go to auction houses. The houses’ power is limited, however, by the demands of the owners, who, in a sellers’ market, keep pressuring the experts to raise estimates. Their ambitions, in turn, are limited by the willingness of billionaires to be strung along. A balance of sorts is thus established. For artists whose work has been promoted in recent years, power is spread differently. German-American artist Lyonel Feininger offers an interesting case. Achim Moeller, of New York, the scholarly dealer preparing Feininger’s catalogue raisonné, by definition knows more than anyone else about the whereabouts of the artist’s paintings and also about the collectors with the experience and the millions needed to play a role.

Knowledge triumphs most decisively in Old Masters. A tiny number of collectors worldwide with the wealth to back up their connoisseurship are immensely influential. So are the very few museum directors and curators who have the requisite visual knowledge as well as a private collector’s hunting instinct and freedom of movement; the remarkable Frits Duparc, who will be retiring at the end of the year as director of the Mauritshuis, in the Hague, is the quintessential example. Add to that number a handful of specialized connoisseur dealers who are preeminent in their fields: Johnny Van Haeften, of London, with his eye for quality and condition, outguns anyone else in Dutch and Flemish works; in Florence, Fabrizio Moretti’s passion for Italian Renaissance masters, backed by sophisticated art historical competence, makes him the dominant force in that area. Finally, the author of the latest monograph on any given Old Master or on a closely defined school plays a significant role. For a 17th-century Spanish still life, U.S. scholar Bill Jordan’s seal of approval can be the difference between triumph and failure.