Book excerpt: Seeks answers to these questions using the underlying assumption that consciousness can be understood using the intellectual potential of modern physics and other sciences. There are a number of theories of consciousness, some based on classical physics while others require the use of quantum concepts. The latter ones have drawn criticism from the parts of the scientific establishment while simultaneously claiming that classical approaches are doomed to failure. The contributing authors presents a spectrum of opinions from both sides of this on-going scientific debate, allowing readers to decide for themselves which of the approaches are most likely to succeed.