difference between the motion picture and TV, or between a 
Corvair and a Volkswagen, for this difference is not between 
two visual spaces, but between tactile and visual ones. A tent 
or a wigwam is not an enclosed or visual space. Neither is a 
cave nor a hole in the ground. These kinds of space—the tent, 
the wigwam, the igloo, the cave—are not “enclosed” in the 
visual sense because they follow dynamic lines of force, like a 
triangle. When enclosed, or translated into visual space, 
architecture tends to lose its tactile kinetic pressure. A square 
is the enclosure of a visual space; that is, it consists of space 
properties abstracted from manifest tensions. A triangle 
follows lines of force, this being the most economical way of 
anchoring a vertical object. A square moves beyond such 
kinetic pressures to enclose visual space relations, while 
depending upon diagonal anchors. This separation of the visual 
from direct tactile and kinetic pressure, and its translation into