Nearly a half century ago, at the dawn of an era renowned for its utopian dreams and dystopian diagnoses, a journalist who loved the American city wrote an attack on all the professional planners and idealists who believed they could design the perfect urban habitat, the city beautiful, a metropolitan Eden.

Forget it, was the message Jane Jacobs elegantly hammered home in that 1961 book, “The Death and Life of Great American Cities.” There is no utopia to be found. And every fantasy of such a paradise — the Modernist towers of Le Corbusier, the Garden Cities of Ebenezer Howard, the cleared slums and ribboned roadways of Robert Moses — has led to urban desolation and ruin. At the time she wrote her book, cities were beginning to totter like drunken derelicts seeking lampposts for support.

As an exhibition opening today at the Municipal Art Society reminds us, Jane Jacobs did not believe that planners could ever restore life to American cities. Instead she put her faith in the chaos of urban life, in diversity, in people — the grocery store owner, the young mother, the child playing in the street, the watchful busybodies leaning out of windows. Cities were at their best, she wrote, when the “ballet of the sidewalks” was evident, a dance that was intrinsically “spontaneous and untidy.” Her prescription was simply not to get in its way.