334
leads to a contradiction between the equalization of spatial
transitions on the one hand and the growing and ever more
differentiated insertion of thresholds on the other. A thresh-
old need not involve walls or doors, but only an air curtain- at least the term should be conceived quite broadly. The
overcoming of an obstacle need not be involved; thresholds
already exist where the edge of a roof separates a covered
zone from one that is set under open sky, where a shadowed
space is set off in relation to sun-filled surroundings, or a type
of flooring contrasts with another one. Sound islands generat-
ed through Muzak are delimited, as are light or door islands.
Beginning with Modernism, architectural boundaries
were produced to a diminishing degree by monolithic ma-
sonry, by delimiting interior and exterior from one another
with single screens whose openings contain simple thresholds.
Instead, the wall was decomposed into different layers, into
filters with a variety of functions: against cold, against noise,
as sun protection, or privacy shields, or to provide hygiene
or security.
The various walls are to some extent staggered in space,
and have differing types of openings. Each forms a different
threshold, each of which is to some extent given a different
placement, and between which threshold spaces are created.
There is also a multiplicity of spatial boundary areas or zones
of admission that require special types of thresholds, for ex-
ample supermarket checkouts, counters in libraries or banks,
ticket offices, or various types of identity checks. Correspond-
ing to various functions, there are special threshold types
whose diversity goes far beyond the traditional architectural
types, for example the crowd control barrier, turnstile or air-
lock. Laurent Stalder has discussed the consequences of the
dissemination of threshold situations for use and perception.
People who move continually between various thresholds
‘no longer know the difference between inside and outside,
but exist in a permanent in-between; no longer experience
boundaries, but only possible margins; no longer experience