Challenging clothes — thank God! Because fashion needs challenge. Often when clothes appear demanding on the runway it’s the result of savvy styling that adds detachable outrage to tried-and-true silhouettes. Not so at Jil Sander, where Raf Simons delivered another stunner, one all about cut, shape and zero models — only panache. Simons’ boldest gestures are genuine proposal rather than ruse. He started from the couture sensibility of spring, but here invoked the precision bravado of Sixties haute in a lineup focused firmly on daywear. Two lean black stirrup-pant looks introduced a chic ski motif anchored by techno-pinhead hooded sweaters — part of a major knit story that included abstract intarsias and waffled pullovers. He then stated his expansion plan. The clothes were, well, big, sometimes shockingly so, cut in dense, solid, bold-toned fabrics with considerable self-structure. Simons amped the volume with a broadened dropped shoulder that fell into neat folds in back. He used this technique for coats and dresses, and while he sometimes contained the shape with loose half-belts in front or back, he never disguised it. Rather, he found alternate ways to expand, even puffing up some dresses and separates with down. Difficult? Most girth-enhancing ideas are. Volume is not an easy sell these days, nor can everyone wear it. Ditto solid blocks of brights. No matter how much fashion professionals might invoke the need for color, seeing someone in neck-to-knee marigold or fire-engine red tends to startle. By working his collection around major volume and bold color (along with gorgeous teal, gray and black), Simons is taking a firm stance against mass luxury. High fashion, he’s suggesting, needs some high-mindedness.