To fully grasp how revolutionary is the work in the Museum of Modern Art's stunning "Picasso: Guitars 1912-1914," which opens Sunday, you should stop and look at Rodin's "Monument to Balzac" (1891) in the museum's sculpture garden before going up to the exhibition on the third floor. Masterpiece though it is, the Rodin epitomizes the "old way" of art that Picasso and his collaborator Georges Braque (whose work isn't a part of this exhibition) overturned in the first two decades of the 20th century, thus setting the stage for most of what followed. In the Rodin, we have a recognizable image, in this case a portrait of an individual. The sculpture is a monolith, its continuous, uniform "skin" clearly separating it from the space around it, and the figure's base setting it off from the world we inhabit. The work was made as sculpture had been for centuries, by modeling the figure in plaster or clay and then casting it in the "noble" material of bronze. Literally and figuratively, all that explodes once we enter the exhibition upstairs. In the 70-odd paintings, collages and sculptures arrayed here, all made in the two-year period that inaugurated the second—or "synthetic"—phase of Cubism, the forms of guitars primarily, but also of bottles, glasses and tables, have been opened out, broken up and recomposed as planar constructions. Space, painted or real, flows through and around them. The sculptures aren't separated from us by bases—they are placed directly on the wall, thus sharing our space. The works were made using nontraditional materials such as sand, cardboard, pins, sheet metal and wallpaper, and the sculptures, rather than being carved or modeled, were made using a technique invented by Picasso himself: assemblage. The guitar was the perfect subject for Picasso, combining the widest possible range of reference with virtually limitless formal possibilities. It linked him to tradition, stringed instruments having been a staple of still-life painting in 17th-century Holland and elsewhere. A quintessentially Spanish image, it functioned as an autobiographical emblem. It was the ideal vehicle for the kind of sexual pun that became a staple of Picasso's art, a suggestively female body conjoined to a phallic neck. (Lest the point be lost on the viewer, Picasso almost always depicted his guitars in a vertical position.) Lastly, the instrument's broad surfaces, taut contours and mysterious interior made it the ideal foil in an artistic language of planes, lines and shifting spaces. Foil and catalyst. Looking at the works installed here it's hard to imagine Picasso achieving his artistic breakthrough using any other motif. "Picasso: Guitars 1912-1914" was organized by Anne Umland and Blair Hartzell, respectively curator and curatorial assistant in the museum's painting and sculpture department. Its centerpiece is the "Still Life with 'Guitar'" of fall 1913, the first work we encounter on entering the exhibition. The work consists of a cardboard guitar and, projecting below it, another cardboard form representing part of a tabletop. "Guitar'" had been donated to the museum in the early 1970s by Picasso and arrived disassembled in a box. It was later put back together and exhibited, but without the tabletop element. That lay forgotten until 2005, when it was rediscovered by a University of Pennsylvania art historian studying a contemporaneous photograph of the sculpture. The complete sculpture is thus now on public view for the first time. Why is the tabletop so important? Because of the way it alters the character of the entire composition. The purpose of the base in "Balzac" and sculptures like it was to clearly identify the statue as "art"—something removed from everyday life. The table top's function is more subtle and complex: It shifts the guitar from being part of our shared space into a quasi-fictive realm, as if it and the guitar were elements in a painted still life. To see for yourself, first look at the "Guitar" while holding up your hand to block out the table top; then move your hand out of the way. The difference in perception is unmistakable. This fusion of multiple levels of reality—the combination of, and contradiction between, sculpture and painting, the real and the illusionistic—is the essence of what Picasso is up to here. As he later put it to his paramour Françoise Gilot: "I'm out to fool the mind rather than the eye. And that goes for sculpture, too." It's also the essence of the liberating transformation he wrought on 20th-century art. Looking at the labels, you realize with a shock that in little more than a year from now most of the works in this show will be 100 years old. Therein lies a paradox of our cultural life: So much of the contemporary work shown in galleries and museums like MoMA, and lauded as revolutionary, quickly looks dated. Yet in its freshness, its bold inventiveness and its ability to engage and surprise us, this work looks contemporary, even timeless.