“We live as we dream – alone.”
(Joseph Conrad, ‘Heart of Darkness’ (1899))
The sceptical Problem Of Other Minds will be solved by biotechnology. Compare people born without a corpus callosum to connect their cerebral hemispheres, or “split brain” patients who’ve had their corpus callosum surgically severed to treat epilepsy. If one hemisphere entertains doubts whether the other hemisphere is really conscious (aka the Problem Of Other Hemispheres), then currently the sceptical hemisphere can’t prove the sentience of its twin. However, advanced biotech promises corpora callosa grown to order, laying sceptical doubts to rest. More radically, artificially-grown corpora callosa and reversible thalamic bridges will let neurotypical humans partially “mind-meld” like the conjoined Hogan sisters today. So yes, solipsism can, in principle, be scientifically disproved.
Mind-melding won’t be technically easy. Are there other objective tests of consciousness?
This is a contentious issue. On standard materialist assumptions, i.e. the formalism of quantum field theory describes fields of insentience, there is no scientific touchstone of consciousness. If physicists and chemists are correct about the fundamental properties of energy and matter, then we should all be p-zombies. First-person facts shouldn’t exist. One’s own mind is the anomaly. Eliminative materialists bite the bullet and claim that humans are p-zombies – although eliminativists disbelieve in their own minds, too, so they aren’t solipsists. Here let’s assume that science should be empirically adequate; most of us struggle to feign anaesthesia. A monistic materialist ontology – as distinct from monistic physicalist ontology – can’t be reconciled with the empirical evidence, i.e. one’s own experience. Dualism and mysterianism lead nowhere. By contrast, non-materialist physicalism is not just empirically adequate, but also has explanatory and predictive power. I don’t know whether non-materialist physicalism is true – it feels absurd. But speculatively, futuristic cerebroscopes could use molecular matter-wave interferometry to demonstrate the insentience of silicon robots and the sentience of biological nervous systems. On this story, scrambled phase coherence is the hallmark of the zombie. The non-classical interference signature diagnostic of phenomenally-bound minds will disclose a perfect structural match between minds and the formalism of physics. Or rather, I predict a perfect structural match. It’s easy to delude oneself. Yet dualism is crazy too.
Will mind-melding technologies or futuristic neuroscanning (eventually) vindicate common sense?
Not entirely, IMO. Solipsism, i.e. the conjecture one is the only sentient being, should be distinguished from the theory that one inhabits a virtual world populated by zombies. Perceptual direct realists conflate these two theories, so the distinction needs elaboration.
Everyone you meet when you’re dreaming is a zombie. Ascribing consciousness to other organisms on the basis of their similar behaviour is systematically misleading; the argument from analogy fails in dreamworlds. Unless you’re having a lucid dream, you are deceived by phantoms. Dreaming is evolutionarily ancient, so life on Earth supports countless zombie-ridden virtual dreamworlds. What’s more controversial is the nature of waking worlds. The perceptual direct realist believes that waking consciousness confers an ability directly to perceive the local environment, including other people’s bodies – and occasionally their exposed brains, too, in a surgical operating theatre. According to the perceptual direct realist, the observable bodies of other organisms are brute facts about our public macroscopic world; only the consciousness of other organisms in this shared arena is a challenge to prove. By contrast, the inferential realist about the external world believes that awake and dreaming world-simulations alike are populated by zombies. The difference between dreaming and perceptual consciousness is that during waking life the zombies of one’s acquaintance are the avatars of sentient beings whose existence one may infer on theoretical grounds, together with the rest of the cosmos. So the argument from analogy may be invoked with justification, but only to hypothesise other zombie-ridden world-simulations run by minds akin to one’s own, not to anthropomorphise the zombies populating one’s own mind. Kant said as much, though he didn’t talk about zombies. The inferred external world sculpts and partly selects the waking world-simulations run by one’s skull-bound mind. Yet even the seemingly faraway horizon is an intrinsic property of the neocortical matter and energy within one’s transcendental skull. Whereas dreamworlds are autonomous, waking up from sleep reboots one’s world-simulation and brings world-making under tight external control via peripheral nerve inputs. Yet the skull is a windowless prison. “Waking up” doesn’t allow feats of remote viewing or confer any other kinds of psi power. In other words, the solipsist is right to believe that his perceived reality is autobiographical; but he’s wrong to believe he is special. Disposable world-simulations in the guise of external reality are an adaptation of animal life.
Does this diagnosis matter?
Typically, the waking psychosis of perceptual direct realism is better for one’s mental health than inferential realism. In common with e.g. Roko’s Basilisk, the Simulation Argument, Bolzmann Brains and Everettian Quantum Mechanics, the world-simulation model of the human predicament is a meme-hazard. In everyday life, perceptual realism is a healthy psychosis to be encouraged in everyone but the most psychologically robust.
However, intellectually speaking, the conceptual framework of perceptual realism also leads to unfathomable mysteries such as (1) the Hard Problem of consciousness, i.e. how does a lump of neural porridge generate first-person facts? (2) the phenomenal Binding Problem in neuroscience, i.e. why aren’t we micro-experiential zombies composed of membrane-bound pixels of “mind-dust”? and (3) the Measurement Problem in quantum mechanics, i.e. why does the otherwise universally valid superposition principle of QM break down on measurement to yield definite outcomes in accordance with the Born rule? Such mysteries proliferate: they are unanswerable within the conceptual framework of perceptual realism. In my view, scientists should trust the formalism of unmodified and unsupplemented (i.e. unitary-only) quantum mechanics, not folk-realism about perception. Our minds exemplify the superposition principle, not its breakdown. In fairness, this is a controversial position. But when saying anything about consciousness, what isn’t?
Ethically speaking, whether we adopt the conceptual framework of inferential realism or common sense perceptual realism wouldn’t matter if natural selection had optimised our waking world-simulations to mirror things as they are. In some ways, the world-simulations run by scientific rationalists are faithful to the structural-relational properties of inferred extra-cranial reality; hence technological civilisation. In other respects, our world-simulations are egocentric cartoons. Some dark Darwinian minds are probably best left entombed in their skulls. Yet in my view, the reason we should favour the development of mind-melding technologies to breach our solipsistic island-universes isn’t their potential to banish philosophical doubt, or even to overcome semantic solipsism. Rather, the tools of inter-personal and cross-species mind-melding will bring about a revolution in both ethics and decision-theoretic rationality – an artificial distinction born of the skull-bound prison of Darwinian life.