The Laws of the Media have been shaped by 
studying the effects of media, so there is always a 
hidden ground  upon which these effects stand, 
and against which they bounce. That is, the law 
of a medium is a figure interplaying with a ground. 
As with a wheel and an axle, there must be an 
interval between the two in order for the play to 
exist.

Marshall McLuhan, “Laws of the Media,” Marshall  
McLuhan: The Man and His Message , (Golden, 
1989), p. 206.