Sigfried Giedion devotes much of his Introduction to Space, Time and Architecture to the theme of "anonymous history," just as Hans Selye tackled the "pharmacology of dirt," or the whole environment, in The Stress of Life. Giedion approaches the entire man made environment as architecture. Most of this environment is unintended and unplanned, or simply leftover junk from other periods. This anonymous history tends to be "invisible" much as John Cage's Silence consists of all the unintended noise of the environment, or as most poetry consists of all the "unintended meanings" or ambiguities.