Based on biological realism, that is, the philosophical assumption that con-sciousness is a real natural biological phenomenon in the brain, we argue that dreaming is a pure form of phenomenality, and suggest that the dreaming brain could be used as a model system for consciousness. The dreaming brain offers the most challenging model system that represents all the theoretically and philosophically interesting features of consciousness. Although difficult to study experimentally, the dreaming brain is the model system that fully preserves all the essential features of consciousness, and cannot be ignored by any theory that aims to explain consciousness.