or communicating with the system, even if he were conscious of being unable to understand its mode of function.

Interaction, whether explicit or simulated, demands an open and contingent work structure, through which the position of the process is more fundamental than that of the materiality and completion of the work. To the idiosyncratically aesthetic paradigms of interactive works—their virtuality, variability, contingency, and simulation—it is possible to add the following endo-physical characteristica describing and defining that interactive and virtual world of electronic media: meta-experiments possessing external (exo) and interior (endo) sides; model worlds with an accessible interface on which the world is defined; they can have various reality planes; their internal operations adapt to the distortion of perspective (or of action) of the observer. [15] For these reasons, endo-aesthetics and endo-physics alike deal with artificial, interface-based worlds in which one can simultaneously participate (endo) or observe (exo). The properties of the world can be discovered through this dual action of the interactor. «A new technology which, in contrast to all

those already known, changes not just something in the world but the ‹world› itself is coming into view as an intellectual possibility.» [16]

Endo-physics as an aesthetic model

An exemplary demonstration of the integration into computer-simulated systems of the endo-aesthetic notions of the internal and external observer is given by the interactive installation «The Wall, the Curtain (Border, the) technical terminology also: Lascaux» (1994) by Peter Weibel, in which the interactor becomes part of what he observes. That distortion triggered by the observer in the reality of his environment is provoked likewise by an interactor participating in the artificial, interactive system. The expression «rubber wall,» which Weibel used one year earlier, was repeated in the context of this new work: «For once, after all, the inner observer of the universe ought to be able to receive data from the external observer and to cast a glance beyond the local event horizon of his universe, beyond his interface (his rubber wall).» [17] This kind of virtuality is based on something Weibel calls the ‹rainbow phenomenon.›