We have all been stuck at a terrible party. A colleague's birthday, maybe. Or a bad date. Or even the dreaded high school reunion. We can all remember that evening, surrounded by people whom we know, but not really. A beige buffet, warm punch the colour of flesh, groups of people posing for photos like high street dummies, and drunk ‘friends’ chatting nonsense, staring at us like mindless zombies. When we have these feelings of isolation, we may begin to entertain the possibility that other people actually are zombies. It is not too far a stretch of the imagination to conceive that other people could be mindless robots: beings that look and behave like humans, but who have no consciousness or feeling.
Although this might seem like a strange worry to entertain seriously, it has plagued philosophers for centuries. What are minds? And how do I know that others possess them?
Although it's ‘common sense’ that we have a ‘mind’ and that others do too, the notion that others have minds is a surprisingly difficult claim to establish. But why?
In this scientific age, we are moving away from thinking about the mind as non-physical soul: something which might persist after our deaths independently of any physical body. Nevertheless, some of the stoniest scientists admit to the intuition that human consciousness is something ‘beyond’ the physical. It doesn't seem physical. And it appears to be hidden in a way even the brain is not (brains can be revealed, but what someone else experiences necessarily seems to be private to them). How, then, can I know that others have such private inner worlds? Perhaps my friends are zombies after all.
A Hard Problem
A philosophical zombie is a creature that looks, acts, and is physically identical to a human being, but lacks consciousness. The common-sense view is that it's obvious that others have conscious minds. Indeed, the belief in other minds is probably an essential belief for anybody who wants to continue living their everyday life in a sane and functional manner. However, philosophy encourages us to examine even common-sense beliefs with unflinching scrutiny. Just how secure is the assumption that other minds exist, or indeed, our own mind exists, understood as such private inner worlds?
A Lonely Mind
Not only might I doubt whether others have conscious minds, I might also begin to wonder whether even their bodies exist and are also an illusion. With a little philosophical scrutiny, we are confronted with an uncomfortable possibility: that the physical world that we perceive through our senses – including our own body – may be nothing but an illusion. ‘I’ may be nothing but a brain in a jar, in the lab of a mad scientist, who chooses to create these illusions by stimulating my brain with their technology (as in the film The Matrix). While common sense may tell us this is ridiculous, how do we really know that our sensory perceptions don't deceive us in this way? After all, everything would seem the same whether the world I experience is real, or such a lab-induced illusion.
Is there a way out of this terrifying consequence of relentlessly pressing doubt? First, let's begin by examining the scepticism employed by the philosopher and mathematician René Descartes.
Scepticism
In his quest for a firm foundation for knowledge, Descartes invites us to apply scepticism to everything we believe to be true. He urges us methodically to strip back every layer of potential illusion to discover what cannot be doubted – what is certain. Descartes suggests that you can dip your toe in the waters of doubt by applying a simple test to objects in the physical world. Take any solid object that is near to you. Can you be certain that it is real? You cannot. You do not know if you are experiencing a computer-generated Matrix-like illusion right now. Apply this to the whole world around you. Perhaps, Descartes thought, there is just my mind and that of a demon intent on deceiving me. Everything would seem just the same. So how can I tell which scenario is true? It seems I cannot.
Descartes digs deeper, examining our bodies. We cannot be certain that they are real. The mind, however (which Descartes believes to be distinct from the body), is real, he argues. The mind must be real if it is able to formulate these doubts. If I can truthfully say, ‘I am doubting my existence’, then I must exist to do the doubting. It is here that we arrive at Descartes's famous phrase, ‘I think, therefore I am.’
So, good: I can at least be certain I exist. But what of other people? Am I a lonely, floating, immaterial mind? Perhaps the only mind to exist? Perhaps the only thing to exist? The view that only I, as a subject, exists, is known as solipsism.
For Descartes, this radical scepticism is not the end of the story. He is not actually sceptical about the external world and other minds. Having coaxed us down his sceptical rabbit hole, Descartes then attempts to rebuild knowledge of external reality on secure foundations in order to assure us that we can know we're not merely a floating ‘I’ or a brain in a jar.
Can God Save Us?
In order to rebuild the external world, Descartes invokes the help of God. He argues that God must exist if I can conceive of the idea of Him – namely, of a perfect being. We humans know that we are imperfect and incapable of creating such an idea ourselves. Therefore, he argues, a perfect being must exist to place such an idea in us, rather like a trademark. For Descartes, the existence of this perfect, supreme being is a ‘clear and distinct idea’, like a mathematical fact. This is an example of what's known as an ontological argument for God's existence – an argument that relies on reason alone.
Assuming God's existence is established, Descartes then argues that we can be sure the external world – including other minds – exists, because this supreme being would not deceive us. Surely, he says, a perfect God is not an evil demon who will deceive me for his own entertainment.
There is a problem with this reasoning, however. Can I really be certain of God's existence? Without a God in whom we can justifiably place our trust, we are left trapped in Descartes's dark rabbit hole, with nothing but ‘I am thinking, therefore I am.’ The existence of God is a huge and separate debate from our present quest, but as the question is still open, let's apply strict scepticism and assume God cannot prop up Descartes's beliefs about the external world and other minds. For all he knows, Descartes's friends are zombies.
Inferring Other Minds Exist
Can't we reasonably infer that other minds exist? It seems the argument is based on a very weak analogy. True when I am in pain I cry out. I see others cry out, but why is it reasonable for me to believe they are in pain too? We cannot assume that because other humans behave like me, they must be conscious like me. We may be able to accept the certainty that one mind exists (the thinking ‘I’ in ‘I think, therefore I am’), but this other argument for other minds looks poor. It is analogous to arguing that because the first oyster I open has a pearl in it, therefore it's reasonable to suppose the other oysters have pearls in them too. I am generalizing on the basis of just a single case, and that is never reasonable.
Dualism
Let's begin to explore whether there is another solution to this puzzle.
Descartes is famously a dualist. The dualist believes that mind and body are two distinct substances, each capable of existing on its own. The body is material, and the mind is immaterial. An alternative is monism – the view that we are made of one substance. One version of monism is also known as materialism, or the more modern term, physicalism. The physicalist argues that there is no floating mind. I do not possess an immaterial soul. There is no ‘ghost in the machine’, as the twentieth-century thinker Gilbert Ryle describes this mysterious, fictional mind. ‘I’ am a material thing, like everything else in the world. I am conscious, but that consciousness resides within the physical realm.
In a scientific spirit, many have concluded that consciousness simply is neurons firing. My mind is therefore completely accessible to scientists, who can inform me that other people fire neurons like I do, and that other minds do exist. These ‘minds’, however, are nothing but another aspect of our physical bodily function, like food digestion.
What is It Like to Be Conscious?
Despite being attracted to such a scientific view – as expressed by, for example, the scientist Professor Susan Greenfield in her TV series Brain Story (in which she says ‘You are your brain’) we may feel unsatisfied with the idea that the mind is physical. Consciousness is something different, many would argue. We can feel it. There is something more to the human experience. The twentieth-century philosopher Thomas Nagel argues for the existence of this ‘something more’, refusing to accept the physicalist position. He tries to explain the nature of this non-physical something – human consciousness – in his famous article ‘What Is it Like to Be a Bat?’ He argues for the existence of what are often called ‘qualia’. ‘Qualia’ refers to the unique experience of consciousness, the what it is like to feel alive, to experience this smell, that visual perception, and so on. Nagel asks us to imagine what it is like to be a bat. We cannot, of course, experience the sonar experiences of the bat, but we accept that most animals – especially humans – have a subjective experience of consciousness. Physicalists, Nagel argues, are foolish to ignore this subjective, private aspect of consciousness. Just because mental states are by their nature subjective, and cannot be scrutinized objectively by science, does not mean we should discount their existence. The facts about consciousness from the inside, as it were, appear to be facts that exist over and above all the physical facts.
In a similar argument, philosopher Frank Jackson illustrates the idea of qualia by asking us to imagine a neuroscientist called Mary. Mary has lived her whole life in a black and white room. She has access only to black and white television and textbooks. She has never seen colour, but she has studied the science behind human colour perception in great detail. This accomplished neuroscientist understands all physical processes involved when colour is being observed. One day, Mary is released into the real world – the colourful world – and she sees a rose for the first time, burning with scarlet beauty. Through tears of joy, Mary realizes that she has learnt something new. She has learnt what it is like to see colour. This suggests there is something more to consciousness than can ever be known through science. Mary's experience seems to show that there are facts about consciousness that are non-physical facts. Because Mary previously knew all the physical facts.
Mary Wasn't Surprised
Despite such strange and seductive thought experiments, some physicalists do not accept the existence of qualia (and, incidentally, even Jackson no longer finds his own argument convincing). They argue that the Mary argument is misleading. Some suggest that if this Mary truly understood everything that there is to know about colour perception in humans, then she would not, in fact, be met with surprising new knowledge when she saw red for the first time. She would give the beautiful flower an unassuming nod, before continuing with her day. The experience of colour would be exactly as she had expected, based on her in-depth study of human consciousness.
The Mary argument continues to divide opinion. It's unclear if Mary would discover something new and indeed non-physical upon leaving her black and white academic prison.
Philosophical Zombies
Earlier, we entertained the idea that all our friends could be zombies, who do not possess conscious minds. The philosopher David Chalmers asks us to use the idea of zombies in another thought experiment. In his ‘zombies’ argument, he attempts to prove his form of dualism, which is the belief that there are non-physical mental properties. Zombies are creatures that are completely physically identical to humans, but they are soulless, non-conscious beings. Chalmers asks us to imagine a possible world, where zombies walk around, looking and acting like humans, but have no conscious mind. (For anyone who has watched Love Island, this is not too hard to imagine.) If it is conceivable that zombies exist, he says, then this establishes that there are mental properties in addition to the physical. Consciousness is something extra, and therefore at least a kind of dualism is true. There are properties beyond the physical – properties that zombies lack, despite being physically indistinguishable from us.
However, others argue that if there really was a creature which was physically identical to a human, then it would possess consciousness.
A Picture of The Mind
When we think of the mind as something necessarily private and unavailable to others (they only ever get to experience my physical body, and perhaps my brain, etc.), we may seem forced to concede the real possibility that my mind is the only mind, and that all my friends are zombies, and that the physical world is illusory. This picture of the mind as a kind of secret inner kingdom, possessing a kind of privacy that no mere physical thing could possess, also seems to result in us being imprisoned in it, unable ever to escape or know what lies outside its strange, metaphysically unbreachable walls. For all we know, solipsism is true.
But perhaps there is something wrong with this picture of the mind which in turn gives rise to these seemingly intractable philosophical puzzles? Perhaps we went wrong in thinking of ourselves in this way. Perhaps the picture is confused? That at least is what several philosophers have suggested, including Ludwig Wittgenstein in his later philosophy. On the other hand, there are philosophers who think that nothing could be more obvious than that we do have these private worlds – after all I can be mistaken about whether there is a real object in front of me, but I cannot be mistaken about that – the appearance of such an object before my mind's eye.
