Steven Rose in The Guardian:
Yet another book about consciousness? These days it seems no self-respecting neuroscientist should be without at least one book-length stab at explaining how the brain enables that most central, if elusive, feature of what makes us human. This is Susan Greenfield’s second. Yet, as she reminds us, it has only been in the last few decades that consciousness studies, once regarded as the province of philosophers, and off-limits for neuroscience, has become a cottage industry for brain researchers, oblivious to the sceptics who joke that the initiator of this new wave was an anaesthesiologist, Stuart Hameroff, whose day job ought surely to be elucidating the processes through which people become unconscious.
This origin may help explain why many brain researchers have such a narrow definition of consciousness, understood by Greenfield, in common with her many peers, as what we retain while awake and lose while asleep or anaesthetised. Such a restricted description raises many questions about this protean term. Can there be consciousness in the abstract, distinct from being conscious of something? Awareness is only one of the several meanings the OED ascribes to consciousness, including self-knowledge and, to me the most important, “the totality of the impressions, thoughts, and feelings, which make up a person’s conscious being”. Neuroscientists are rarely trained in philosophy, but a little modesty might not go amiss. Some committed reductionists among them maintain that consciousness is merely a “user illusion” – that you may think you are making conscious decisions but in “reality” all the hard work is being done by the interactions of nerve cells within the brain. Most, however, are haunted by what their philosophical sympathisers call the “hard problem” of the relationship between objective measures – say of light of a particular wavelength – and qualia, the subjective experience of seeing red.