This midi skirt by Theory pairs classic pleats with a flattering A-line silhouette and an easy pull-on elastic waistband for effortless style. This midi skirt by Theory pairs classic pleats with a flattering A-line silhouette and an easy pull-on elastic waistband for effortless style. Established in 1997, New York-based Theory creates cool, expertly tailored clothing from the finest materials designed to inspire how you feel, work, and live.