New York's Theory label was set up in 1997 and has proven to be one of the most enduringly popular names in fashion. This is in no small part due to the simple, clean aesthetic that creates contemporary silhouettes that appeal to a broad range of women. The label has a low key style but doesn't shy away from being bold, whether that's with respect to the use of colors or incorporating the odd subtle print. When it comes to tailoring and cool, collected separates Theory is the obvious choice for a sleek, modern closet. The flats line from Theory includes cozy wool slippers, espadrilles and loafers.