Visual form depends upon three variables: light, the position of the beholder, and the particular relation with the environment. We empirically reinterpret the image into an idea of corporeality, and this defines the form of the space within. We thus grasp its spiritual import, its content, and its meaning. Windows form the rhythmical articulation of light and dark in the façade, which determines the character more directly than the sum total of all columns, ornaments and cornices. To see architecture means to draw together into a single mental image the series of these dimensionally interpreted images that are present to us as we walk through interior spaces and round their exterior shells. It is light that first rounds out mathematical precision and space consciousness to the freedom, independence and law of architectonic creation.