Sir Roger Penrose (b. 8 August 1931 in Colchester, England) is, in the physics textbook, the man of the singularity theorems, the Penrose diagrams, twistor theory, the aperiodic Penrose tilings – and since October 2020 Nobel laureate in physics for the mathematical demonstration that black holes are a robust consequence of the general theory of relativity. What does exist in the physics textbook but is set aside as a "side work": Penrose is the only living Nobel laureate in physics with an independently worked-out quantum-mechanical theory of consciousness – Orchestrated Objective Reduction (Orch-OR), jointly with the American anaesthesiologist Stuart Hameroff from 1996. Penrose is expressly not a theist but a secular Platonist – and is thus the crucial proof for one point of our series: the post-1906 pattern is not about religion but about the insistence on non-material reality. Penrose takes mathematical structures and consciousness as ontologically real seriously, without letting them be reduced to matter – and is thus a secularist who nonetheless stands in the same series as Heisenberg, Bohm and Eccles.
Who is Penrose?
Born on 8 August 1931 in Colchester, Essex, into an extraordinary family: father Lionel S. Penrose was a medic and geneticist, mother Margaret Leathes a physician; the elder brother Oliver Penrose is a statistical physicist, the younger brother Jonathan Penrose was ten times British chess champion. Lionel and Roger together designed in the 1950s the famous Penrose staircase and the Penrose triangle – the optical-impossibility figures that M. C. Escher later worked into his prints Ascending and Descending (1960) and Waterfall (1961).
Bachelor of mathematics at University College London 1952, doctorate in algebraic geometry at St John's College, Cambridge, under W. V. D. Hodge and John A. Todd 1958. Various positions in the 1960s (Cambridge, Birkbeck College London, Princeton, Cornell, Austin/Texas). From 1973 Rouse Ball Professor of Mathematics at Oxford; emeritus there since 1998. Penrose is Honorary Fellow at Wadham College, Oxford, and at St John's College, Cambridge. Knighthood 1994, Order of Merit 2000, Copley Medal 2008, Nobel Prize in Physics 2020.
Singularity theorems and the 2020 Nobel Prize
In 1965 Penrose published in Physical Review Letters a three-page proof that for the first time treated the general theory of relativity with global geometrical methods: under physically plausible conditions, every gravitational collapse must lead to a mathematical singularity – a point in the spacetime continuum at which the curvature diverges. With this it was for the first time demonstrated that black holes in general relativity are not special cases of idealised spherical configurations but a generic consequence of the theory. In the following years Stephen Hawking and Penrose extended the method to the Big Bang (Hawking-Penrose theorems 1970), with the result: the beginning of our universe too must, in standard relativity, be a singularity.
For this work Penrose received in 2020, aged 89, the Nobel Prize in Physics – jointly with Reinhard Genzel and Andrea Ghez, who had detected the supermassive black hole Sagittarius A* at the centre of our galaxy. In the Nobel committee's citation Penrose's theorem was characterised as "the first new prediction of general relativity since Einstein himself". Penrose received half the prize, the other half being shared by Genzel and Ghez.
Main mathematical works
A brief overview of further Penrose contributions to mathematical physics – without the consciousness line, just the mathematical material:
- Penrose diagrams (1964) – today's standard graphical representation of the global structure of spacetime manifolds in general relativity.
- Twistor theory (from 1967) – an alternative mathematical formalism in which the elementary objects are not spacetime points but "twistors". The theory has, in the last 20 years, found new attention in string theory and in quantum field theory (amplituhedron, twistor string theory).
- Penrose tilings (1974) – aperiodic tilings of the plane with only two tile shapes that never generate a periodic repetition. The tilings became a surprising bridge into materials physics when Dan Shechtman in 1982 experimentally discovered quasicrystals with the same aperiodic symmetry – for which Shechtman received the 2011 Nobel Prize in Chemistry.
- Penrose process (1969) – the possibility of extracting energy from a rotating black hole without touching the mass-energy itself.
- Conformal Cyclic Cosmology (CCC, from 2010) – Penrose's late cosmological hypothesis that our universe is a phase within a sequence of conformal cycles. The CCC is controversial in cosmology but published as a serious hypothesis in specialist journals.
Penrose is thus not an outsider but one of the central mathematical figures of theoretical physics of the second half of the 20th century. With this background he entered the consciousness debate in 1989 – with the weight of an already established mathematician of the highest rank.
The Emperor's New Mind (1989)
In 1989 Penrose published with Oxford University Press a book that made him widely known well beyond academic physics: The Emperor's New Mind. Concerning Computers, Minds, and the Laws of Physics. 466 pages, of which about two thirds are a popular-scientific introduction to quantum mechanics, general relativity, thermodynamics and computability theory – and a concluding third with Penrose's actual thesis.
The thesis has two cumulative steps:
- Step 1: Consciousness is non-algorithmic. Penrose advances a mathematical argument on the basis of Gödel's incompleteness theorem (1931). Gödel's theorem shows that in every sufficiently rich formal system there are true mathematical statements that cannot be proved within the system. Penrose argues that a human mathematician can nevertheless see such statements to be true – thus reaches beyond the means of the formal system. But if human thinking were a Turing-equivalent algorithmic operation, it could not do that. Conclusion: human consciousness must have non-algorithmic components. Today's Artificial Intelligence (AI) in the classical computer sense cannot in principle reproduce consciousness, not merely in fact.
- Step 2: The non-algorithmic component points to new physics. If consciousness is not produced by classical algorithms, something must happen physically in our brain that cannot be described by standard quantum mechanics. Penrose conjectures that this something has to do with the still-missing unification of quantum mechanics and general relativity – that is, with quantum gravity.
The book became an international bestseller, enthusiastically praised by some mathematicians and philosophers, sharply criticised by many AI researchers and cognitive scientists. The Gödel step in particular has sparked its own philosophical debate that continues to this day.
Objective Reduction (OR) and the quantum-gravity hypothesis
In 1994 Penrose deepened his position in the sequel Shadows of the Mind. A Search for the Missing Science of Consciousness (Oxford). Here he formulated the specifically physical component of his hypothesis: Objective Reduction or OR – the idea that the "collapse" of a quantum wave function is an objective physical process (not merely a consequence of observation) and that this collapse is gravity-induced.
Penrose's proposal in short: a quantum-mechanical system in superposition – such as a mass superposed in two different positions – represents, because of general relativity, a superposition of two different spacetime geometries. The energy difference between these geometries has a characteristic time τ ≈ ℏ/E. When this time becomes shorter than the lifetime of the quantum state, the superposition collapses by itself, without an observer. The collapse is objective and gravity-induced. Penrose has further formulated the proposal in several follow-up publications; it is today the subject of experimental tests (Marshall, Bouwmeester et al., various mesoscopic quantum-optics experiments since the late 2000s).
Hameroff, microtubules and Orch-OR (from 1996)
In 1992 the American anaesthesiologist Stuart Hameroff (b. 1947, professor of anaesthesiology at the University of Arizona, Tucson) read The Emperor's New Mind and contacted Penrose. Hameroff had been working since the 1980s on microtubules – those tiny, hollow protein tubes in the cytoskeleton of every eukaryotic cell, which occur particularly densely in nerve cells and are involved in signal transmission and in synaptic plasticity. Hameroff had the idea that microtubules might perform quantum computations – as "quantum computers inside the nerve cell".
From the encounter grew Orchestrated Objective Reduction (Orch-OR), which Hameroff and Penrose have worked out since 1996 in a long series of papers. The core idea combines both theories:
- Quantum-coherent superpositions arise in the tubulin proteins of the microtubules of neuronal cells.
- These superpositions are "orchestrated" by the surrounding brain tissue (hence the O in Orch-OR) – that is, their formation and topology depend on neuronal activity.
- The superpositions collapse by Penrose's OR mechanism, gravity-induced, once the critical time threshold is reached.
- Each such OR event in an orchestrated microtubule system corresponds to an elementary moment of conscious experience.
The thesis has since been further developed in numerous papers, summarised in the 2014 review article in Physics of Life Reviews"Consciousness in the universe: A review of the 'Orch OR' theory". The paper was commented on by a dozen prominent commentators with their own replies – more than the usual peer-review discussion of a specialist topic, and an indication of the scientific visibility of the hypothesis.
Criticism and experimental findings
The central criticism of Orch-OR was formulated in 2000 by MIT physicist Max Tegmark: in the warm, wet milieu of a mammalian brain (body temperature 37 °C, high ion density) quantum-mechanical superpositions should decohere within 10⁻²⁰ seconds – far too fast to reach the time scales necessary for Orch-OR (10⁻²⁰ s to 10⁻⁴ s, a difference of sixteen orders of magnitude). Hameroff and Penrose responded to this in detail in 2014 and proposed mechanisms by which microtubules could form isolated quantum islands inside the cell.
The experimental situation has in the 2010s and 2020s shifted partly in favour of Orch-OR:
- 2014: Anirban Bandyopadhyay (NIMS Tsukuba) and collaborators reported experimental evidence for quantum-coherent oscillations in the megahertz and kilohertz ranges in microtubules, in agreement with predictions from Hameroff and Penrose.
- 2022: Cui & the Hameroff group published experimental findings that anaesthetics exert their effect through interventions in microtubule structures – a central indicator finding, because anaesthesia is the only reversibly and reproducibly controllable intervention in conscious experience.
- 2023–2025: Several working groups (Wellcome / Tibbits, Hameroff & collaborators, others) have reported in Drosophila and in mammalian neurons evidence for quantum-mechanical properties in microtubules that are incompatible with Tegmark's original decoherence prediction.
These experimental indications have not freed Orch-OR from the status of "controversial hypothesis". They show, however, that the theory was not – as many critics had claimed – disposed of by a single physical order-of-magnitude estimate. The question is open and currently active research.
Penrose the Platonist – not a theist
Here Penrose shows a decisive difference from almost all other cases of our series. Penrose has been asked publicly several times whether he believes in God – and has just as many times publicly denied it. He describes himself as an atheist or agnostic in the traditional sense. But: he is an explicit Platonist about mathematics, and thus not a materialist.
In The Road to Reality (Jonathan Cape 2004), his 1099-page main work on the overall presentation of theoretical physics, Penrose sketches a three-worlds ontology that structurally resembles Karl Popper's and John Eccles' model, but differs in emphasis:
- World 1: the physical world.
- World 2: the mental world of conscious experience.
- World 3: the Platonic world of mathematical forms.
These three worlds are, on Penrose's view, all ontologically real and hang together in a peculiar circular relation: the physical world appears to be governed by the mathematical forms (laws of nature are mathematical). The mental world arises within the physical world (brains are part of physics). The mathematical forms are recognised by the mental world (mathematicians discover theorems). With that the circle closes. Penrose calls this mutual dependence explicitly a mystery which he does not try to dissolve – but he insists that none of the three worlds is reducible to one of the others.
With that Penrose is the most important supporting case for the point that the position "non-material reality is real" need not be religious. Heisenberg's central order, Bohm's implicate order, Schrödinger's singular consciousness and Penrose's Platonic World 3 are different languages for a structurally similar position: there is more than matter, and this more is knowable and describable.
Position in the pattern
Penrose is in our post-1906 series the case that places the thesis most cleanly on a secular basis. His profile:
- Highest professional reputation: Nobel Prize in Physics 2020, Order of Merit, Knighthood, Rouse Ball Professor at Oxford. No one can dismiss him as an "extra-scientific speculator".
- Independent quantum theory of consciousness: Orch-OR has been published since 1996, is peer-reviewed in Physics of Life Reviews, has experimental consequences, has been taken increasingly seriously since 2014. Penrose is the only living Nobel laureate in physics with such a theory.
- Secular position: No theism, no religious vocabulary, no revival experience. The position is mathematical Platonism + non-reductionism + quantum mechanics. With this Penrose shows that the series is not religiously defined.
- Mechanism of marginalisation: As with Heisenberg, the downplaying of the reach. Orch-OR is in textbooks (or not), is occasionally mentioned in overviews, is marked "speculative" in many Wikipedia versions – but the fact that a Nobel laureate in physics has tenaciously held and developed it over three decades does not penetrate the picture of the "mainstream consensus".
What remains
- The quantum-consciousness hypothesis is in play. With Penrose's voice and with the Stuart Hameroff microtubule hypothesis there exists a scientifically serious, peer-reviewed, in-principle experimentally testable position that does not reduce consciousness to classical neuronal computation. Beck-Eccles 1992 (see our Eccles article) and Hameroff-Penrose from 1996 are the two great independent proposals of this kind from the 1990s.
- The Gödel step is serious. Whatever one thinks of its success: Penrose's argument that human mathematical insight has non-algorithmic components is a worked-out philosophical position that is seriously discussed in the philosophy of logic (Lucas, the Penrose-Lucas argument).
- Platonism is a serious ontology. Penrose is not the only significant mathematician who holds the Platonist position – Gödel himself, Cantor, Hardy and more recently Hugh Woodin are further prominent voices. That mathematical forms are ontologically real belongs to the legitimate dispute of the philosophy of mathematics.
- The extension of the pattern line. With Penrose the series leaves the religiously-traditioned vocabulary completely. With this it becomes visible that what the series has in common is not a confessional creed but the refusal of materialist reduction – including in its secular-mathematical form.
- Line to Eccles, Bohm, Heisenberg. Penrose completes the six-person cluster of worked-out quantum-consciousness proposals of the late 20th century: Wigner 1961 (philosophical), Bohm 1980 (ontological), Beck-Eccles 1992 (neuroscientific), Hameroff-Penrose from 1996 (physical-anaesthesiological). For the institutional background see our article on Mediumship and Power.
Including Penrose does not mean judging the singularity theorems or twistor theory differently. It means reading them in the theoretical framework in which their originator has worked for almost four decades – a framework in which the mathematical world, the physical world and the consciously experienced world form three independent, ontologically real spheres whose mediation is the open research problem. Whoever omits this from the reading reads not Penrose but a reception.
Sources
- Roger Penrose: The Emperor's New Mind. Concerning Computers, Minds, and the Laws of Physics. Oxford University Press, Oxford 1989.
- Roger Penrose: Shadows of the Mind. A Search for the Missing Science of Consciousness. Oxford University Press, Oxford 1994.
- Roger Penrose: The Large, the Small and the Human Mind. Cambridge University Press, Cambridge 1997 (Tanner Lectures 1995, with contributions by Stephen Hawking, Abner Shimony and Nancy Cartwright).
- Roger Penrose: The Road to Reality. A Complete Guide to the Laws of the Universe. Jonathan Cape, London 2004 (1099 pages; Penrose's main work of overall presentation of theoretical physics).
- Roger Penrose: Cycles of Time. An Extraordinary New View of the Universe. Bodley Head, London 2010 (Conformal Cyclic Cosmology).
- Stuart Hameroff & Roger Penrose: Consciousness in the universe: A review of the "Orch OR" theory. Physics of Life Reviews 11, 2014, pp. 39–78 (with commentaries).
- Roger Penrose: Nobel Lecture "Black Holes, Cosmology, and Space-Time Singularities", Stockholm 2020.
- R. Penrose: Gravitational Collapse and Space-Time Singularities. Physical Review Letters 14, 1965, pp. 57–59 (the central Nobel-Prize paper).
- Max Tegmark: Importance of quantum decoherence in brain processes. Physical Review E 61, 2000, p. 4194 – the central criticism of Orch-OR.
- Anirban Bandyopadhyay et al.: Atomic water channel controlling remarkable properties of a single brain microtubule. Scientific Reports 4, 2014 – the experimental microtubule findings.
- Stuart Hameroff: website hameroff.faculty.arizona.edu.