Ideal criticism, Baudelaire wrote, is “partiale, passionnée, politique”—“subjective, impassioned, committed.” Add “conversational, opinionated, informal” and you have a description of the writings of the man who could be called the first modern art critic, the great eighteenth-century philosophe Denis Diderot. Diderot’s detailed reports on the “Salons”—vast exhibitions, held at the Louvre, of works by members of the Royal Academy of Painting and Sculpture— hold their own with the liveliest, most personal documents of the period, and, at the same time, point ahead to such nineteenth-century efforts as the art writing of Baudelaire or Stendhal. Composed equally of meticulous observation, unabashed value judgments, uninhibited digressions, and outrageous asides, Diderot’s “Salons” vividly bring to life the taste, aesthetic arguments, and obsessions of an entire era. They are also models of vigorous, flexible language, a French that is elegantly refined and wholly natural, cultivated and informal, either all at the same time or with one mode dominating, according to what is suitable to the subject. Even a cursory reading of these trenchant chronicles makes it easy to understand why their author was celebrated for his brilliant conversation. Great stuff, in other words.

In Diderot’s lifetime, these remarkable essays remained unknown to the public, since they were written for a private manuscript newsletter, Correspondance littéraire, edited in Paris by an expatriate German and circulated through diplomatic channels; its subscribers, never more than fifteen at a time, included the rulers of Russia, Poland, and Sweden, the Grand Duke of Tuscany, and