Roger Penrose On Why Consciousness Does Not Compute

A Nautilus profile/interview by Steve Paulson (originally 2017). Penrose — celebrated for work on general relativity, black holes, twistor theory, and Penrose tiles — defends his “audacious and quite possibly crackpot” theory of consciousness. Conventional wisdom: “The theory is almost certainly wrong, but Penrose is brilliant, so we’d be foolish to dismiss it out of hand.”

The core claim

• Penrose starts from the premise that consciousness is non-computational and lies beyond what current neuroscience, biology, or physics can explain.
• “We need a major revolution in our understanding of the physical world in order to accommodate consciousness” — and the most likely place to find it, short of leaving physics entirely, is in making sense of quantum mechanics.
• Even a complete map of neurons, synapses, and neurotransmitters wouldn’t obviously explain how “3 pounds of wet tissue” generates subjective thought and feeling. Something is missing (echoing Chalmers’ “fundamental property” idea and the “mysterians”).

Orch-OR (Orchestrated Objective Reduction)

• Developed with anesthesiologist Stuart Hameroff.
• Draws on quantum computing: qubits in superposition (multiple states at once) before coalescing; quantum coherence = many particles acting in one quantum state.
• Hameroff’s contribution: coherence occurs in microtubules — tubular protein structures in neurons’ cytoskeletons — whose symmetry and lattice structure Penrose thinks “reeks of something quantum mechanical,” and which may be shielded from neuronal noise.
• “Objective Reduction” ties to Penrose’s ideas about quantum gravity (how superposition applies to spacetime geometries), a theory he considers still undiscovered. Moments of conscious awareness are “orchestrated” by microtubules storing and processing information.

The critiques

• Too warm and wet: most scientists think quantum coherence needs frigid, protected environments. Max Tegmark calculated coherence in microtubules would break down in ~100 quadrillionths of a second — implying you’d need ~10^13 thoughts per second for thought to be quantum computation.
• Stephen Hawking (Penrose’s old collaborator) was dubious: “consciousness is a mystery and quantum gravity is another mystery so they must be related.” Penrose says their real disagreement is about the nature of quantum mechanics.
• 2013 Japanese experiments reported detecting vibrations in microtubules, which Penrose and Hameroff took as support that the brain isn’t too noisy for quantum activity.

Penrose’s intellectual roots

• Gödel’s incompleteness theorem (encountered as a Cambridge grad student): some mathematical truths can’t be proven — “whatever is going on in our understanding is not computational.” This became the spine of his argument.
• Weirdness of quantum theory (via Dirac’s lectures; Schrödinger’s cat): major figures like Schrödinger, Dirac, and Einstein were themselves troubled — suggesting to Penrose that quantum theory is incomplete and “needs to be superseded.” His leap: the brain exploits where quantum mechanics goes wrong, requiring a new science that doesn’t yet exist.
• His 1989 book The Emperor’s New Mind was prompted by Marvin Minsky’s claim that the brain is “just a computer made of meat.” Minsky, by contrast, called consciousness a “suitcase word” and famously dismissed it as “what people wasted their time on in the 20th century.”

The odd couple, and the appeal

• Hameroff is upfront about spiritual views (soul surviving death); Penrose is an atheist and self-described “very materialistic and physicalist kind of person,” uneasy about New Agers co-opting quantum non-locality.
• Why root for him anyway: “The science of consciousness feels stuck, and here’s a theory — however speculative — that suggests a possible way forward.” But it may ask too much (quantum coherence in microtubules and undiscovered laws of physics), and even if confirmed, it might only push the mystery deeper into a “quantum mind-body problem.”

Metaphysical tail

• Penrose posits “proto-consciousness” whenever a quantum decision is made in the universe (e.g. a dust speck resolving from superposition to one location) — a possible “free choice,” though he professes not to know.
• On free will: not quite endorsing it — the choices “look random,” but he wonders whether free will is something more subtle than either determinism or randomness, “a delicate borderline.”
• Surprising closing note: “Somehow, our consciousness is the reason the universe is here.” He suspects conscious life is rare, and muses that our universe may not be especially “favorably disposed toward consciousness.”