You know you can’t go wrong with these objects because they’re all museum pieces. All, in fact, are on display now at New York’s Cooper-Hewitt Museum, which, as very few people know, is also the Smithsonian Institution’s National Museum of Design. This diverting new show is drawn from a collection of some 250,000 objects founded in 1897 by the three Hewitt sisters, granddaughters of the industrialist Peter Cooper. Judging from the displays, the sisters were acquisitors of vast and occasionally eccentric enthusiasms. They and their successors appear to have amassed the world’s definitive collection of wallpaper, for instance. It is easy to imagine that the five decorative tassels in a discreet wall case near the entrance are the tips of a vast and justifiably little-explored iceberg of passementerie. If the Smithsonian proper is the nation’s attic, the Cooper-Hewitt is more like a stuffy Victorian parlor, every surface of which has been subjected to intensive, third-degree decoration. But the show, which will run through August 1992 with rotating exhibits, is a good introduction to this vast and little-known collection, housed in Andrew Carnegie’s stupendous turn-of-the-century mansion on upper Fifth Avenue. You can’t really blame the Cooper-Hewitt for trying to fulfill its role as what director Dianne Pilgrim calls “the national museum of something that no two people can agree on the meaning of.”

Which is why the lay visitor may find the most interesting part of the exhibit in several rooms near the end, which show various design solutions to three mundane challenges of modern life: seating the body, providing artificial light and conveying food and drink to the mouth. The variety of shapes and materials that have been used to support the human backside is extraordinary. Here is Massimo Vignelli’s Handkerchief Chair, looking like a square of wet tissue that has been thrown against a metal frame and miraculously hardened into the contours of a human bottom; here is Frank Gehry’s sinuous easy chair of corrugated cardboard, just the thing for stretching out (preferably in long pants and sleeves) with a nice cold … oops, sorry, Frank. Does it… rot? Here is a sconce that appears to have been inspired by newspapers blown against a wall, and numerous black metal lamps, ingeniously cantilevered and hinged and counter weighted, with names like Dove and Jazz. Here are Carlo Moretti’s beautiful drinking glasses, whose bias-cut lips probably make for a lot of amusement at the expense of guests who mistakenly drink from the low side; here, also, is the mystery of why square plates, which obviously are much more space-efficient to stack than round ones, have never caught on. (Of 18 place settings on display, 15 are more or less round, one is square, one octagonal and one triangular.) Here, too, is … holy cow, Lydia, don’t we have those in the country house? Sure you do; they’re Fjord cutlery, whose gently rounded stainless-steel tines and bowls and comfortable teak handles were one of the great design cliches of the ’80s. A genuine museum piece.

That’s the great thing about design; if you’re alive in the 20th century, you’re already a collector.