In 1973 Mangold created at least four versions of Circle In and Out of a Polygon; two were executed on canvas and two on Masonite. In all four the interior graphite line becomes interchangeable with the top, left, and bottom borders of the support. Similarly, half of the circle is outlined on the acrylic surface, while the other half continues as the curved edge on the painting’s right. Mangold challenges his viewers to mentally reverse such images in order to comprehend the compositional nuances of the geometric abstraction. It is this emphasis on the conceptual basis of vision that truly links Mangold to the Minimalists, who brought their audiences to an unprecedented level of perceptual awareness.