In a Romanesque church, light is something distinct from 
     and contrasting with the heavy, somber, tactile 
     substance of the walls. The Gothic wall seems to be 
     porous: light filters through it, permeating it, merging 
     with it, transfiguring it. . . . Light, which is ordinarily 
     concealed by matter, appears as the active principle; and 
     matter is aesthetically real only insofar as it partakes of, 
     and is defined by, the luminous quality of light. . . . In this 
     decisive aspect, then, the Gothic may be described as 
     transparent, diaphanous architecture.

These effects of diaphanous stone are obtained by stained 
glass, but they are quite relevant to the medieval approach to 
the human senses and to the senses of scripture above all. It is 
interesting that Simson points out the tactile quality of stone. 
An oral manuscript culture had no fear of tactility, the very