If Olivier Theyskens was going to do what he was aspiring to do with Theyskens’ Theory this season -that is, design a collection in which each piece was so completely essential to it and within a woman’s wardrobe, that excluding even one from the group would be impossible- then he would need to be rigorous, precise, and ready to edit. “I was inspired by the way that Theory is, always so engineered and crisp, and I wanted to bring that to the Theyskens’ customer” the designer said during Monday’s preview. “I wanted the line to be neater. I wanted definition in the styles. And I killed a lot of colors because it’s really just about black, white, some blue, some jeans and a print.”