Let’s deal with the unpleasantness first. Since 2010, commercial worth has replaced aesthetic value for a much publicized sector of the art world. In large centers, wealthy mega-galleries have taken over real estate and inflated sometimes questionable reputations, although, happily, splendid artists, such as Thomas Nozkowski and Martin Puryear, among others, have also benefited from their attention. Midrange galleries, however, have succumbed to the pressures of unreasonable rents, leaving accomplished artists without representation....