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Sunday, September 21, 2014

Hard problem of consciousness

Hard problem of consciousness

From Wikipedia, the free encyclopedia
The hard problem of consciousness is the problem of explaining how and why we have qualia or phenomenal experiences — how sensations acquire characteristics, such as colours and tastes.[1] David Chalmers, who introduced the term "hard problem" of consciousness,[2] contrasts this with the "easy problems" of explaining the ability to discriminate, integrate information, report mental states, focus attention, etc. Easy problems are easy because all that is required for their solution is to specify a mechanism that can perform the function. That is, their proposed solutions, regardless of how complex or poorly understood they may be, can be entirely consistent with the modern materialistic conception of natural phenomena. Chalmers claims that the problem of experience is distinct from this set, and he argues that the problem of experience will "persist even when the performance of all the relevant functions is explained".[3]

The existence of a "hard problem" is controversial and has been disputed by some philosophers.[4][5] Providing an answer to this question could lie in understanding the roles that physical processes play in creating consciousness and the extent to which these processes create our subjective qualities of experience.[3]

Several questions about consciousness must be resolved in order to acquire a full understanding of it. These questions include, but are not limited to, whether being conscious could be wholly described in physical terms, such as the aggregation of neural processes in the brain. If consciousness cannot be explained exclusively by physical events, it must transcend the capabilities of physical systems and require an explanation of nonphysical means. For philosophers who assert that consciousness is nonphysical in nature, there remains a question about what outside of physical theory is required to explain consciousness.

Formulation of the problem

Chalmers' formulation

In Facing Up to the Problem of Consciousness, Chalmers wrote:[3]

Easy problems

Chalmers contrasts the Hard Problem with a number of (relatively) Easy Problems that consciousness presents. (He emphasizes that what the easy problems have in common is that they all represent some ability, or the performance of some function or behavior).
  • the ability to discriminate, categorize, and react to environmental stimuli;
  • the integration of information by a cognitive system;
  • the reportability of mental states;
  • the ability of a system to access its own internal states;
  • the focus of attention;
  • the deliberate control of behavior;
  • the difference between wakefulness and sleep.

Other formulations

Various formulations of the "hard problem":
  • "How is it that some organisms are subjects of experience?"
  • "Why does awareness of sensory information exist at all?"
  • "Why do qualia exist?"
  • "Why is there a subjective component to experience?"
  • "Why aren't we philosophical zombies?"
James Trefil notes that "it is the only major question in the sciences that we don't even know how to ask."[6]

Historical predecessors

The hard problem has scholarly antecedents considerably earlier than Chalmers.

Gottfried Leibniz wrote, as an example also known as Leibniz's gap:
Moreover, it must be confessed that perception and that which depends upon it are inexplicable on mechanical grounds, that is to say, by means of figures and motions. And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception.[7]
Isaac Newton wrote in a letter to Henry Oldenburg:
to determine by what modes or actions light produceth in our minds the phantasm of colour is not so easie.[8]
T.H. Huxley remarked:
how it is that any thing so remarkable as a state of consciousness comes about as the result of irritating nervous tissue, is just as unaccountable as the appearance of the Djin when Aladdin rubbed his lamp.[9]

Responses

Scientific attempts

There have been scientific attempts to explain subjective aspects of consciousness, which is related to the binding problem in neuroscience. Many eminent theorists, including Francis Crick and Roger Penrose, have worked in this field. Nevertheless, even as sophisticated accounts are given, it is unclear if such theories address the hard problem. Eliminative materialist philosopher Patricia Smith Churchland has famously remarked about Penrose's theories that "Pixie dust in the synapses is about as explanatorily powerful as quantum coherence in the microtubules."[10]

Consciousness is fundamental or elusive

Some philosophers, including David Chalmers and Alfred North Whitehead, argue that conscious experience is a fundamental constituent of the universe, a form of panpsychism sometimes referred to as panexperientialism. Chalmers argues that a "rich inner life" is not logically reducible to the functional properties of physical processes. He states that consciousness must be described using nonphysical means. This description involves a fundamental ingredient capable of clarifying phenomena that has not been explained using physical means. Use of this fundamental property, Chalmers argues, is necessary to explain certain functions of the world, much like other fundamental features, such as mass and time, and to explain significant principles in nature.

Thomas Nagel has posited that experiences are essentially subjective (accessible only to the individual undergoing them), while physical states are essentially objective (accessible to multiple individuals). So at this stage, we have no idea what it could even mean to claim that an essentially subjective state just is an essentially non-subjective state. In other words, we have no idea of what reductivism really amounts to.[11]

New mysterianism, such as that of Colin McGinn, proposes that the human mind, in its current form, will not be able to explain consciousness.[12]

Deflationary accounts

Some philosophers, such as Daniel Dennett,[4] Stanislas Dehaene,[5] and Peter Hacker,[13] oppose the idea that there is a hard problem. These theorists argue that once we really come to understand what consciousness is, we will realize that the hard problem is unreal. For instance, Dennett asserts that the so-called hard problem will be solved in the process of answering the easy ones.[4] In contrast with Chalmers, he argues that consciousness is not a fundamental feature of the universe and instead will eventually be fully explained by natural phenomena. Instead of involving the nonphysical, he says, consciousness merely plays tricks on people so that it appears nonphysical—in other words, it simply seems like it requires nonphysical features to account for its powers. In this way, Dennett compares consciousness to stage magic and its capability to create extraordinary illusions out of ordinary things.[14]

To show how people might be commonly fooled into overstating the powers of consciousness, Dennett describes a normal phenomenon called change blindness, a visual process that involves failure to detect scenery changes in a series of alternating images.[15] He uses this concept to argue that the overestimation of the brain's visual processing implies that the conception of our consciousness is likely not as pervasive as we make it out to be. He claims that this error of making consciousness more mysterious than it is could be a misstep in any developments toward an effective explanatory theory. Critics such as Galen Strawson reply that, in the case of consciousness, even a mistaken experience retains the essential face of experience that needs to be explained, contra Dennett.

To address the question of the hard problem, or how and why physical processes give rise to experience, Dennett states that the phenomenon of having experience is nothing more than the performance of functions or the production of behavior, which can also be referred to as the easy problems of consciousness.[4] He states that consciousness itself is driven simply by these functions, and to strip them away would wipe out any ability to identify thoughts, feelings, and consciousness altogether. So, unlike Chalmers and other dualists, Dennett says that the easy problems and the hard problem cannot be separated from each other. To him, the hard problem of experience is included among—not separate from—the easy problems, and therefore they can only be explained together as a cohesive unit.[14]

Dehaene's argument has similarities with those of Dennett. He says Chalmers' 'easy problems of consciousness' are actually the hard problems and the 'hard problems' are based only upon intuitions that, according to Dehaene, are continually shifting as understanding evolves. "Once our intuitions are educated ...Chalmers' hard problem will evaporate" and "qualia...will be viewed as a peculiar idea of the prescientific era, much like vitalism...[Just as science dispatched vitalism] the science of consciousness will eat away at the hard problem of consciousness until it vanishes."[5]

Like Dennett, Peter Hacker argues that the hard problem is fundamentally incoherent and that "consciousness studies," as it exists today, is "literally a total waste of time:"[13]
“The whole endeavour of the consciousness studies community is absurd – they are in pursuit of a chimera. They misunderstand the nature of consciousness. The conception of consciousness which they have is incoherent. The questions they are asking don’t make sense. They have to go back to the drawing board and start all over again.”
Critics of Dennett's approach, such as David Chalmers and Thomas Nagel, argue that Dennett's argument misses the point of the inquiry by merely re-defining consciousness as an external property and ignoring the subjective aspect completely. This has led detractors to refer to Dennett's book Consciousness Explained as Consciousness Ignored or Consciousness Explained Away.[4] Dennett discussed this at the end of his book with a section entitled Consciousness Explained or Explained Away?[15]

Glenn Carruthers and Elizabeth Schier argue that the main arguments for the existence of a hard problem -- philosophical zombies, Mary's room, and Nagel's bats -- are only persuasive if one already assumes that "consciousness must be independent of the structure and function of mental states, i.e. that there is a hard problem." Hence, the arguments beg the question. The authors suggest that "instead of letting our conclusions on the thought experiments guide our theories of consciousness, we should let our theories of consciousness guide our conclusions from the thought experiments."[16] Contrary to this line of argument, Chalmers says: "Some may be led to deny the possibility [of zombies] in order to make some theory come out right, but the justification of such theories should ride on the question of possibility, rather than the other way round".[17]:96

A notable deflationary account is the Higher-Order Thought theories of consciousness.[18][19] Peter Carruthers discusses "recognitional concepts of experience", that is, "a capacity to recognize [a] type of experience when it occurs in one's own mental life", and suggests such a capacity does not depend upon qualia.[20] Though the most common arguments against deflationary accounts and eliminative materialism is the argument from qualia, and that conscious experiences are irreducible to physical states - or that current popular definitions of "physical" are incomplete - the objection follows that the one and same reality can appear in different ways, and that the numerical difference of these ways is consistent with a unitary mode of existence of the reality. Critics of the deflationary approach object that qualia are a case where a single reality cannot have multiple appearances. As John Searle points out: "where consciousness is concerned, the existence of the appearance is the reality."[21]

Massimo Pigliucci distances himself from eliminativism, but he insists that the hard problem is still misguided, resulting from a "category mistake":[22]
Of course an explanation isn't the same as an experience, but that’s because the two are completely independent categories, like colors and triangles. It is obvious that I cannot experience what it is like to be you, but I can potentially have a complete explanation of how and why it is possible to be you.
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Quantum mind

Quantum mind

From Wikipedia, the free encyclopedia
The quantum mind or quantum consciousness[1] hypothesis proposes that classical mechanics cannot explain consciousness, while quantum mechanical phenomena, such as quantum entanglement and superposition, may play an important part in the brain's function, and could form the basis of an explanation of consciousness. It is not a single theory, but rather a collection of distinct ideas.

A few theoretical physicists have argued that classical physics is intrinsically incapable of explaining the holistic aspects of consciousness, whereas quantum mechanics can. The idea that quantum theory has something to do with the workings of the mind go back to Eugene Wigner, who assumed that the wave function collapses due to its interaction with consciousness. However, most contemporary physicists and philosophers consider the arguments for an important role of quantum phenomena to be unconvincing.[2] Physicist Victor Stenger characterized quantum consciousness as a "myth" having "no scientific basis" that "should take its place along with gods, unicorns and dragons."[3]

The philosopher David Chalmers has argued against quantum consciousness. He has discussed how quantum mechanics may relate to dualistic consciousness.[4] Indeed, Chalmers is skeptical of the ability of any new physics to resolve the hard problem of consciousness.[5][6]

Description of main quantum mind approaches

David Bohm

David Bohm took the view that quantum theory and relativity contradicted one another, and that this contradiction implied that there existed a more fundamental level in the physical universe.[7] He claimed that both quantum theory and relativity pointed towards this deeper theory, which he formulated in terms of a quantum field theory. This more fundamental level was proposed to represent an undivided wholeness and an implicate order, from which arises the explicate order of the universe as we experience it.

Bohm's proposed implicate order applies both to matter and consciousness, and he suggests that it could explain the relationship between them. Mind and matter are here seen as projections into our explicate order from the underlying reality of the implicate order. Bohm claims that when we look at the matter in space, we can see nothing in these concepts that helps us to understand consciousness.
In trying to describe the nature of consciousness, Bohm discusses the experience of listening to music. He believed that the feeling of movement and change that make up our experience of music derives from both the immediate past and the present both being held in the brain together, with the notes from the past seen as transformations rather than memories. The notes that were implicate in the immediate past are seen as becoming explicate in the present. Bohm views this as consciousness emerging from the implicate order.

Bohm sees the movement, change or flow and also the coherence of experiences, such as listening to music as a manifestation of the implicate order. He claims to derive evidence for this from the work of Jean Piaget[8] in studying infants. He states that these studies show that young children have to learn about time and space, because they are part of the explicate order, but have a "hard-wired" understanding of movement, because it is part of the implicate order. He compares this "hard-wiring" to Chomsky's theory that grammar is "hard-wired" into young human brains.

In his writings, Bohm never proposed any specific brain mechanism by which his implicate order could emerge in a way that was relevant to consciousness, nor any means by which the propositions could be tested or falsified.[citation needed]

Roger Penrose and Stuart Hameroff

Theoretical physicist Roger Penrose and anaesthesiologist Stuart Hameroff collaborated to produce the theory known as Orchestrated Objective Reduction (Orch-OR). Penrose and Hameroff initially developed their ideas separately, and only later collaborated to produce Orch-OR in the early 1990s. The theory was reviewed and updated by the original authors in late 2013.[9][10]
Penrose's controversial argument began from Gödel's incompleteness theorems. In his first book on consciousness, The Emperor's New Mind (1989), he argued that while a formal proof system cannot prove its own inconsistency, Gödel-unprovable results are provable by human mathematicians.[citation needed] He took this disparity to mean that human mathematicians are not describable as formal proof systems, and are not therefore running a computable algorithm.[citation needed]

Penrose determined that wave function collapse was the only possible physical basis for a non-computable process. Dissatisfied with its randomness, Penrose proposed a new form of wave function collapse that occurred in isolation, called objective reduction. He suggested that each quantum superposition has its own piece of spacetime curvature, and when these become separated by more than one Planck length, they become unstable and collapse.[citation needed] Penrose suggested that objective reduction represented neither randomness nor algorithmic processing, but instead a non-computable influence in spacetime geometry from which mathematical understanding and, by later extension, consciousness derived.[citation needed]

Originally, Penrose lacked a detailed proposal for how quantum processing could be implemented in the brain. However, Hameroff read Penrose's work, and suggested that microtubules would be suitable candidates.[citation needed]

Microtubules are composed of tubulin protein dimer subunits. The tubulin dimers each have hydrophobic pockets that are 8 nm apart, and which may contain delocalised pi electrons. Tubulins have other smaller non-polar regions that contain pi electron-rich indole rings separated by only about 2 nm. Hameroff proposes that these electrons are close enough to become quantum entangled.[11] Hameroff originally suggested the tubulin-subunit electrons would form a Bose–Einstein condensate, but this was discredited.[12] He then proposed a Frohlich condensate, a hypothetical coherent oscillation of dipolar molecules. However, this too has been experimentally discredited.[13]

Furthermore, he proposed that condensates in one neuron could extend to many others via gap junctions between neurons, thus forming a macroscopic quantum feature across an extended area of the brain. When the wave function of this extended condensate collapsed, it was suggested to non-computationally access mathematical understanding and ultimately conscious experience, that are hypothetically embedded in the geometry of spacetime.[citation needed]

However, Orch-OR made numerous false biological predictions, and is considered to be an extremely poor model of brain physiology. The proposed predominance of 'A' lattice microtubules, more suitable for information processing, was falsified by Kikkawa et al.,[14][15] who showed that all in vivo microtubules have a 'B' lattice and a seam. The proposed existence of gap junctions between neurons and glial cells was also falsified.[16] Orch-OR predicted that microtubule coherence reaches the synapses via dendritic lamellar bodies (DLBs), however De Zeeuw et al. proved this impossible,[17] by showing that DLBs are located micrometers away from gap junctions.[18]

In January 2014, Hameroff and Penrose announced that the discovery of quantum vibrations in microtubules by Anirban Bandyopadhyay of the National Institute for Materials Science in Japan in March 2013[19] confirms the hypothesis of the Orch-OR theory.[10][20]

Umezawa, Vitiello, Freeman, Kak

Hiroomi Umezawa and collaborators proposed a quantum field theory of memory storage. Giuseppe Vitiello and Walter Freeman have proposed a dialog model of the mind, where this dialog takes place between the classical and the quantum parts of the brain.[21][22] Quantum field theory models of brain dynamics are fundamentally different from the Penrose-Hameroff theory. Subhash Kak has proposed that the physical substratum to neural networks has a quantum basis,[23] but he also points out that the quantum mind will still have machine-like limitations.[24] He points to a role for quantum theory in the distinction between machine intelligence and biological intelligence.[25][26]

Henry Stapp

Henry Stapp favors the idea that quantum waves are reduced only when they interact with consciousness. He argues from the Orthodox Quantum Mechanics of John von Neumann that the quantum state collapses when the observer selects one among the alternative quantum possibilities as a basis for future action. The collapse, therefore, takes place in the expectation that the observer associated with the state.[citation needed]

His theory of how mind may interact with matter via quantum processes in the brain differs from that of Penrose and Hameroff.[27]

Criticism by Max Tegmark

The main argument against the quantum mind proposition is that quantum states in the brain would decohere before they reached a spatial or temporal scale at which they could be useful for neural processing, although in photosynthetic organisms quantum coherence is involved in the efficient transfer of energy, within the timescales calculated by Tegmark.Quantum biology[28] This argument was elaborated by the physicist, Max Tegmark. Based on his calculations, Tegmark concluded that quantum systems in the brain decohere at sub-picosecond timescales commonly assumed to be too short to control brain function.[29][30]
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Roger Penrose

Roger Penrose

From Wikipedia, the free encyclopedia

Sir Roger Penrose
Roger Penrose-6Nov2005.jpg
Roger Penrose, 2005
Born 8 August 1931 (age 83)
Colchester, Essex, England
Residence United Kingdom
Nationality British
Fields Mathematical physics
Institutions
Alma mater
Doctoral advisor John A. Todd
Other academic advisors W. V. D. Hodge
Doctoral students
Known for
Influenced
Notable awards
Notes
He is the brother of Jonathan Penrose, Oliver Penrose and Shirley Hodgson; son of Lionel Penrose; nephew of Roland Penrose.

Sir Roger Penrose OM FRS (born 8 August 1931), is an English mathematical physicist, mathematician and philosopher of science. He is the Emeritus Rouse Ball Professor of Mathematics at the Mathematical Institute of the University of Oxford, as well as an Emeritus Fellow of Wadham College.

Penrose is known for his work in mathematical physics, in particular for his contributions to general relativity and cosmology. He has received a number of prizes and awards, including the 1988 Wolf Prize for physics, which he shared with Stephen Hawking for their contribution to our understanding of the universe.[1]

Early life and academia

Born in Colchester, Essex, England, Roger Penrose is a son of psychiatrist and mathematician Lionel Penrose and Margaret Leathes,[2] and the grandson of the physiologist John Beresford Leathes. His uncle was artist Roland Penrose, whose son with photographer Lee Miller is Antony Penrose. Penrose is the brother of mathematician Oliver Penrose and of chess Grandmaster Jonathan Penrose. Penrose attended University College School and University College, London, where he graduated with a first class degree in mathematics. In 1955, while still a student, Penrose reintroduced the E. H. Moore generalised matrix inverse, also known as the Moore–Penrose inverse,[3] after it had been reinvented by Arne Bjerhammar (1951). Penrose earned his PhD at Cambridge (St John's College) in 1958, writing a thesis on "tensor methods in algebraic geometry" under algebraist and geometer John A. Todd. He devised and popularised the Penrose triangle in the 1950s, describing it as "impossibility in its purest form" and exchanged material with the artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it. Escher's Waterfall, and Ascending and Descending were in turn inspired by Penrose. As reviewer Manjit Kumar puts it:
As a student in 1954, Penrose was attending a conference in Amsterdam when by chance he came across an exhibition of Escher's work. Soon he was trying to conjure up impossible figures of his own and discovered the tri-bar – a triangle that looks like a real, solid three-dimensional object, but isn't. Together with his father, a physicist and mathematician, Penrose went on to design a staircase that simultaneously loops up and down. An article followed and a copy was sent to Escher. Completing a cyclical flow of creativity, the Dutch master of geometrical illusions was inspired to produce his two masterpieces.[4]
In 1965, at Cambridge, Penrose proved that singularities (such as black holes) could be formed from the gravitational collapse of immense, dying stars.[5] This work was extended by Hawking to prove the Penrose–Hawking singularity theorems.
Oil painting by Urs Schmid (1995) of a Penrose tiling using fat and thin rhombi.

In 1967, Penrose invented the twistor theory which maps geometric objects in Minkowski space into the 4-dimensional complex space with the metric signature (2,2). In 1969, he conjectured the cosmic censorship hypothesis. This proposes (rather informally) that the universe protects us from the inherent unpredictability of singularities (such as the one in the centre of a black hole) by hiding them from our view behind an event horizon. This form is now known as the "weak censorship hypothesis"; in 1979, Penrose formulated a stronger version called the "strong censorship hypothesis". Together with the BKL conjecture and issues of nonlinear stability, settling the censorship conjectures is one of the most important outstanding problems in general relativity. Also from 1979 dates Penrose's influential Weyl curvature hypothesis on the initial conditions of the observable part of the Universe and the origin of the second law of thermodynamics.[6] Penrose and James Terrell independently realised that objects travelling near the speed of light will appear to undergo a peculiar skewing or rotation. This effect has come to be called the Terrell rotation or Penrose–Terrell rotation.[7][8]
A Penrose tiling

Penrose is well known for his 1974 discovery of Penrose tilings, which are formed from two tiles that can only tile the plane nonperiodically, and are the first tilings to exhibit fivefold rotational symmetry. Penrose developed these ideas based on the article Deux types fondamentaux de distribution statistique[9] (1938; an English translation Two Basic Types of Statistical Distribution) by Czech geographer, demographer and statistician Jaromír Korčák. In 1984, such patterns were observed in the arrangement of atoms in quasicrystals.[10] Another noteworthy contribution is his 1971 invention of spin networks, which later came to form the geometry of spacetime in loop quantum gravity. He was influential in popularising what are commonly known as Penrose diagrams (causal diagrams).

In 1983, Penrose was invited to teach at Rice University in Houston, by the then provost Bill Grodon. Roger Penrose worked at Rice University form 1983 to 1987.[11]

Later activity

In 2004 Penrose released The Road to Reality: A Complete Guide to the Laws of the Universe, a 1,099-page book aimed at giving a comprehensive guide to the laws of physics. He has proposed a novel interpretation of quantum mechanics.[12]

Penrose is the Francis and Helen Pentz Distinguished (visiting) Professor of Physics and Mathematics at Pennsylvania State University.[13] He is also a member of the Astronomical Review Editorial Board.

An earlier universe

WMAP image of the (extremely tiny) anisotropies in the cosmic background radiation

In 2010, Penrose reported possible evidence, based on concentric circles found in WMAP data of the CMB sky, of an earlier universe existing before the Big Bang of our own present universe.[14] He mentions this evidence in the epilogue of his 2010 book Cycles of Time,[15] a book in which he presents his reasons, to do with Einstein's field equations, the Weyl curvature C, and the Weyl curvature hypothesis, that the transition at the Big Bang could have been smooth enough for a previous universe to survive it. He made several conjectures about C and the WCH, some of which were subsequently proved by others, and the smoothness is real. In simple terms, he believes that the singularity in Einstein's field equation at the Big Bang is only an apparent singularity, similar to the well-known apparent singularity at the event horizon of a black hole. The latter singularity can be removed by a change of coordinate system, and Penrose proposes a different change of coordinate system that will remove the singularity at the big bang. This was a daring step, relying on certain conjectures being proved, but these have subsequently been proved.[citation needed] One implication of this is that the major events at the Big Bang can be understood without unifying general relativity and quantum mechanics, and therefore we are not necessarily constrained by the Wheeler–DeWitt equation, which disrupts time.

Physics and consciousness

Prof. Penrose at a conference.

Penrose has written books on the connection between fundamental physics and human (or animal) consciousness. In The Emperor's New Mind (1989), he argues that known laws of physics are inadequate to explain the phenomenon of consciousness. Penrose proposes the characteristics this new physics may have and specifies the requirements for a bridge between classical and quantum mechanics (what he calls correct quantum gravity). Penrose uses a variant of Turing's halting theorem to demonstrate that a system can be deterministic without being algorithmic. (For example, imagine a system with only two states, ON and OFF. If the system's state is ON when a given Turing machine halts and OFF when the Turing machine does not halt, then the system's state is completely determined by the machine; nevertheless, there is no algorithmic way to determine whether the Turing machine stops.)

Penrose believes that such deterministic yet non-algorithmic processes may come into play in the quantum mechanical wave function reduction, and may be harnessed by the brain. He argues that the present computer is unable to have intelligence because it is an algorithmically deterministic system. He argues against the viewpoint that the rational processes of the mind are completely algorithmic and can thus be duplicated by a sufficiently complex computer. This contrasts with supporters of strong artificial intelligence, who contend that thought can be simulated algorithmically. He bases this on claims that consciousness transcends formal logic because things such as the insolubility of the halting problem and Gödel's incompleteness theorem prevent an algorithmically based system of logic from reproducing such traits of human intelligence as mathematical insight. These claims were originally espoused by the philosopher John Lucas of Merton College, Oxford.

The Penrose/Lucas argument about the implications of Gödel's incompleteness theorem for computational theories of human intelligence has been widely criticised by mathematicians, computer scientists and philosophers, and the consensus among experts in these fields seems to be that the argument fails, though different authors may choose different aspects of the argument to attack.[16] Marvin Minsky, a leading proponent of artificial intelligence, was particularly critical, stating that Penrose "tries to show, in chapter after chapter, that human thought cannot be based on any known scientific principle." Minsky's position is exactly the opposite – he believes that humans are, in fact, machines, whose functioning, although complex, is fully explainable by current physics. Minsky maintains that "one can carry that quest [for scientific explanation] too far by only seeking new basic principles instead of attacking the real detail. This is what I see in Penrose's quest for a new basic principle of physics that will account for consciousness."[17]

Penrose responded to criticism of The Emperor's New Mind with his follow up 1994 book Shadows of the Mind, and in 1997 with The Large, the Small and the Human Mind. In those works, he also combined his observations with that of anesthesiologist Stuart Hameroff.

Penrose and Hameroff have argued that consciousness is the result of quantum gravity effects in microtubules, which they dubbed Orch-OR (orchestrated objective reduction). Max Tegmark, in a paper in Physical Review E,[18] calculated that the time scale of neuron firing and excitations in microtubules is slower than the decoherence time by a factor of at least 10,000,000,000. The reception of the paper is summed up by this statement in Tegmark's support: "Physicists outside the fray, such as IBM's John A. Smolin, say the calculations confirm what they had suspected all along. 'We're not working with a brain that's near absolute zero. It's reasonably unlikely that the brain evolved quantum behavior'".[19] Tegmark's paper has been widely cited by critics of the Penrose–Hameroff position.

In their reply to Tegmark's paper, also published in Physical Review E, the physicists Scott Hagan, Jack Tuszynski and Hameroff[20][21] claimed that Tegmark did not address the Orch-OR model, but instead a model of his own construction. This involved superpositions of quanta separated by 24 nm rather than the much smaller separations stipulated for Orch-OR. As a result, Hameroff's group claimed a decoherence time seven orders of magnitude greater than Tegmark's, but still well short of the 25 ms required if the quantum processing in the theory was to be linked to the 40 Hz gamma synchrony, as Orch-OR suggested. To bridge this gap, the group made a series of proposals. It was supposed that the interiors of neurons could alternate between liquid and gel states. In the gel state, it was further hypothesized that the water electrical dipoles are oriented in the same direction, along the outer edge of the microtubule tubulin subunits. Hameroff et al. proposed that this ordered water could screen any quantum coherence within the tubulin of the microtubules from the environment of the rest of the brain. Each tubulin also has a tail extending out from the microtubules, which is negatively charged, and therefore attracts positively charged ions. It is suggested that this could provide further screening. Further to this, there was a suggestion that the microtubules could be pumped into a coherent state by biochemical energy.
Roger Penrose in the University of Santiago de Compostela to receive the Fonseca Prize.

Finally, it is suggested that the configuration of the microtubule lattice might be suitable for quantum error correction, a means of holding together quantum coherence in the face of environmental interaction. In the last decade, some researchers who are sympathetic to Penrose's ideas have proposed an alternative scheme for quantum processing in microtubules based on the interaction of tubulin tails with microtubule-associated proteins, motor proteins and presynaptic scaffold proteins. These proposed alternative processes have the advantage of taking place within Tegmark's time to decoherence.

Hameroff, in a lecture in part of a Google Tech talks series exploring quantum biology, gave an overview of current research in the area, and responded to subsequent criticisms of the Orch-OR model.[22] In addition to this, a recent 2011 paper by Roger Penrose and Stuart Hameroff gives an updated model of their Orch-OR theory, in light of criticisms, and discusses the place of consciousness within the universe.[23]

Phillip Tetlow, although himself supportive of Penrose's views, acknowledges that Penrose's ideas about the human thought process are at present a minority view in scientific circles, citing Minsky's criticisms and quoting science journalist Charles Seife's description of Penrose as "one of a handful of scientists" who believe that the nature of consciousness suggests a quantum process.[19]

In January 2014 Hameroff and Penrose announced that a discovery of quantum vibrations in microtubules by Anirban Bandyopadhyay of the National Institute for Materials Science in Japan[24] confirms the hypothesis of Orch-OR theory.[25] A reviewed and updated version of the theory was published along with critical commentary and debate in the March 2014 issue of Physics of Life Reviews.[26]

Personal life

Family life

Penrose is married to Vanessa Thomas, head of mathematics at Abingdon School,[27][28] with whom he has one son.[27] He has three sons from a previous marriage to American Joan Isabel Wedge, whom he married in 1959. He is the elder brother of Jonathan Penrose, the chessplayer.

Religious views

Penrose does not hold to any religious doctrine,[29] and refers to himself as an atheist.[30] In the film A Brief History of Time, he said, "I think I would say that the universe has a purpose, it's not somehow just there by chance ... some people, I think, take the view that the universe is just there and it runs along – it's a bit like it just sort of computes, and we happen somehow by accident to find ourselves in this thing. But I don't think that's a very fruitful or helpful way of looking at the universe, I think that there is something much deeper about it."[31] Penrose is a Distinguished Supporter of the British Humanist Association.

Awards and honours

Roger Penrose during a lecture

Penrose has been awarded many prizes for his contributions to science. He was elected a Fellow of the Royal Society of London in 1972. In 1975, Stephen Hawking and Penrose were jointly awarded the Eddington Medal of the Royal Astronomical Society. In 1985, he was awarded the Royal Society Royal Medal. Along with Stephen Hawking, he was awarded the prestigious Wolf Foundation Prize for Physics in 1988. In 1989 he was awarded the Dirac Medal and Prize of the British Institute of Physics. In 1990 Penrose was awarded the Albert Einstein Medal for outstanding work related to the work of Albert Einstein by the Albert Einstein Society. In 1991, he was awarded the Naylor Prize of the London Mathematical Society. From 1992 to 1995 he served as President of the International Society on General Relativity and Gravitation. In 1994, Penrose was knighted for services to science.[32] In the same year he was also awarded an Honorary Degree (Doctor of Science) by the University of Bath.[33] In 1998, he was elected Foreign Associate of the United States National Academy of Sciences. In 2000 he was appointed to the Order of Merit. In 2004 he was awarded the De Morgan Medal for his wide and original contributions to mathematical physics. To quote the citation from the London Mathematical Society:
His deep work on General Relativity has been a major factor in our understanding of black holes. His development of Twistor Theory has produced a beautiful and productive approach to the classical equations of mathematical physics. His tilings of the plane underlie the newly discovered quasi-crystals.[34]
In 2005 Penrose was awarded an honorary doctorate by Warsaw University and Katholieke Universiteit Leuven (Belgium), and in 2006 by the University of York. In 2008 Penrose was awarded the Copley Medal. He is also a Distinguished Supporter of the British Humanist Association and one of the patrons of the Oxford University Scientific Society. In 2011, Penrose was awarded the Fonseca Prize by the University of Santiago de Compostela. In 2012, Penrose was awarded the Richard R. Ernst Medal by ETH Zürich for his contributions to science and strengthening the connection between science and society.

Works

Forewords to Beating the Odds: The Life and Times of E. A. Milne, written by Meg Weston Smith. Published by World Scientific Publishing Co in June 2013.
Penrose also wrote forewords to Quantum Aspects of Life and Anthony Zee's book Fearful Symmetry (foreword).
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