Symbolism perhaps suffers from middle-child syndrome. From the storied vanguardism of its older sibling, Impressionism, to the legendary antics of its younger ones, Fauvism and Cubism, it can be easy to forget the febrile movement that reared its head from the late 1880s into the early 1900s. The firstborn and the babies share a family resemblance: The eldest child—who pushed the limits of perception and paint—sees his work, a few decades later, taken to new heights in the hands of the youngest. That, at least, is the story of modernism—a tale in which Symbolism, with its embarrassing fixation on figuration, sometimes schlocky tropes, and an arsenal of abstruse references, has no place.

If Symbolism is cursed first with forgettability, it is afflicted next with ill-definition. And if the former is a quirk of art historiography, the latter can be laid squarely at the feet of its hand-waving theorists, who declaimed it with gusto if not always lucidity. Like many middle children, Symbolism was more concerned with defining itself against its predecessor than in actually defining itself. Emerging from a moment when modern life had come to feel especially incoherent, Symbolism made a credo of doubt, uncertainty, and mystery.

It was born, as the poet Jean Moréas declared in 1886, an avowed “enemy of didaction, declamation, false sensibility and objective description,” but wha...