Maddox, a former editor of Nature which, with Science , is the foremost scientific journal in the world, wrote that 'No amount of introspection can enable a person to discover just which set of neurons in which part of his or her head is executing some thought-process. Such information seems to be hidden from the human user.' Colin McGinn, a British philosopher at Rutgers University, New Jersey, argues that consciousness is resistant to explanation, in principle and for all time.19 Other philosophers, such as Harvard's Thomas Nagel and Hilary Putnam, argue that at present (and maybe for all time) science cannot account for 'qualia', the first-person phenomenal experience that we understand as consciousness, why, in Simon Blackburn's words, the grey matter of the brain can provide us with the experience of, for example, yellow-ness. Benjamin Libet, in a series of controversial experiments, has claimed that it takes about half a second for consciousness itself to happen ('Libet's delay'). Whether this (if true) is an advance is not yet clear. John Gray, professor of European thought at the London School of Economics, is one of those who has identified such phenomena as the 'hard problem' in consciousness studies.20 On the other hand, John Searle, Mills Professor of philosophy at the University of California, Berkeley, says there is nothing much to explain, that consciousness is an 'emergent property' that automatically arises when you put 'a bag of neurons' together. He explains, or tries to, by analogy: the behaviour of H2O molecules 'explains' liquidity, but the individual molecules are not liquid-this is another emergent property.21 (Such arguments are reminiscent of the 'pragmatic' philosophy of William James and Charles Peirce, discussed in Chapter 34, where the sense of self emerges from behaviour, not the other way round.) Roger Penrose, a physicist from London University, believes that a new kind of dualism is needed, that in effect a whole new set of physical laws may apply inside the brain, which account for consciousness. Penrose's particular contribution is to argue that quantum physics operates inside tiny structures, known as tubules, within the nerve cells of the brain to produce-in some as yet unspecified way-the phenomena we recognise as consciousness.22 Penrose actually thinks that we live in three worlds-the physical, the mental and the mathematicaclass="underline" 'The physical world grounds the mental world, which in turn grounds the mathematical world and the mathematical world is the ground of the physical world and so on around the circle.'23 Many people, who find this tantalising, nonetheless don't feel Penrose has proved anything. His speculation is enticing and original, but it is still speculation. Instead, it is two forms of reductionism that, in the present climate, attract most support. For people like Daniel Dennett, a biologically-inclined philosopher from Tufts University near Boston in Massachusetts, human consciousness and identity arise from the narrative of our lives, and this can be related to specific brain states. For example, there is growing evidence that the ability to 'apply intentional predicates to other people is a human universal' and is associated with a specific area of the brain (the orbitofrontal cortex), an ability which in certain states of autism is defective. There is also evidence that the blood supply to the orbitofrontal cortex increases when people 'process' intentional verbs as opposed to non-intentional ones and that damage to this area of the brain can lead to a failure to introspect. Other experiments have shown that activity in the area of the brain known as the amygdala is associated with the experience of fear, that the decisions of individual monkeys in certain games could be predicted by the firing patterns of individual neurons in the orbitofrontal-striatal circuits of the brain, that neurotransmitters known as propranolol and serotonin affect decision-making, and that the ventral putamen within the striatum is activated when people experience pleasure.24 Suggestive as this is, it is also the case that the micro-anatomy of the brain varies quite considerably from individual to individual, and that a particular phenomenal experience is represented at several different points in the brain, which clearly require integration. Any 'deep' patterns relating experience to brain activity have yet to be discovered, and seem to be a long way off, though this is still the most likely way forward. A related approach-and this is perhaps to be expected, given other developments in recent years-is to look at the brain and consciousness in a Darwinian light. In what sense is consciousness adaptive? This approach has produced two views-one, that the brain was in effect 'jerry built' in evolution to accomplish very many and very different tasks. On this account, the brain is at base three organs, a reptilian core (the seat of our basic drives), a palaeomammalian layer, which produces such things as affection for offspring, and a neomammalian brain, the seat of reasoning, language and other 'higher functions'.25 The second approach is to argue that throughout evolution (and throughout our bodies) there have been emergent properties: for example, there is always a biochemical explanation underlying a physiological or medical