Emotions influence behavior that alters the state of consciousness. Bhairava is the ultimate form of manifestation or pure "I" consciousness. It signifies the essence of the ultimate reality, consciousness or Atman. Delirium is a syndrome encompassing disturbances in attention, consciousness, and cognition. Anthroposophy describes a broad evolution of human consciousness. Transpersonal anthropology studies the relationship between altered states of consciousness and culture. Can something exist without being perceived by consciousness? It is possible to define life in terms of consciousness. Within each personal consciousness thought is always changing. It incorporates themes relating to philosophy, class consciousness, and personal conflict. Signs include loss of consciousness and abnormal or absent breathing. Samkhya school espouses dualism between consciousness and matter. This led to numerous theories about reactionary consciousness. "free will", explaining them as inventions of the moral consciousness. Yoga is therefore seen as a process of interiorization or ascent of consciousness.