Virtual Reality Art involves the design of artificial worlds that offer new experiences to spectators. An important aspect for the development of VR Art installations is the principled definition of behaviour for the environment as a whole, which would facilitate experiments with alternative laws of physics, time, and causality. We describe the first results of an ongoing project dedicated to the development of software tools for the use of Intelligent Virtual Environments in VR Art. Using the architecture of a state-of-theart game engine, we have developed Artificial Intelligence techniques that support the definition of alternative laws of physics. After discussing the principles behind alternative reality we describe two complementary modes of description for alternative behaviour: qualitative physics and causal simulation. This is illustrated by examples integrated into the virtual environment. Categories and Subject Descriptors H5.1 [MultiMedia Information Systems] Artificial, Au...