In a chapter in The Descent of Man (1871-77) on the question of how “mental powers” evolved from the simplest animals to humans, Charles Darwin was worried that it was so complex it might never be solved.
Progress is being made but the working of the human brain, especially consciousness, remains one of the two great unsolved problems in biology; the other is the emergence of life about 4 billion years ago. The brain is also one of the great unsolved problems of philosophy (and psychology), where it is usually called the mind.
The big divide in philosophy lies between the materialists – for example, Toland, Hume, James and Ayer – and the immaterialists – for example, Descartes and Berkeley. Materialists believe that the brain is just another part of the body which has various functions such as thought, being, self-consciousness, communication, especially using language etc.
Modern materialists say that the brain is made of cells containing atoms and molecules; the bits follow the laws of nature, that is, of chemistry, physics and genetics. There is only one kind of world, the material world, and all kinds of activity including mental activity depend only on changes in the state of the bits of that world.
Most scientists are materialists, though almost all would say that they have very little idea how the brain works. It is obvious it is an electrochemical machine, but no materialist has yet explained with any precision what thought or consciousness is.
The immaterialists, originally influenced by religious ideas of the supernatural, immortality and the soul, believe that each person is essentially a self-conscious being, the self, who is immaterial and may be immortal. The self resides in our material body. The immaterial mind that is self-conscious, it thinks, and it is the self that defines our being and our relationship with the outside world. Descartes wrote: I think therefore I am.
David Berman, a distinguished philosopher, has been at Trinity College since coming from New York in the mid-1960s to study George Berkeley under AA Luce. Lunchtime conversations with David have been among the most enjoyable of my academic life.
He has been engrossed in the puzzle that is consciousness. In his beautifully written, succinct and stimulating book, drawing on his deep appreciation for the history of philosophy, he has set out to settle that big divide in philosophy, and great Irish philosophers have major roles in his story. On the way he makes some challenging proposals to scientists.
He has focussed on two major theories of consciousness: monism and dualism. A monist has only one kind of consciousness, a self-awareness experienced in the process of perceiving things. A dualist has this kind of consciousness and a second kind.
Berman says that a dualist can be “aware of themselves as being different from the objects they perceive”. According to him the dualist can sometimes feel detached from the objects being perceived, that is, they can be self-conscious at the same time as they are conscious of external phenomena. Berman calls this the “core dualistic experience”, an ability to experience mental activity distinct from the objects that are being sensed at the same time.
Berman has devised a questionnaire that allows him to assess whether a person is a monist or a dualist and in a small survey he has found that about half of us are one type and half the other. Berman argues that both ideas of the mind are true in that they exist as the real conscious experiences of two different kinds of people. He summarises this in what he calls the Two Consciousness Theory (2CT). Berman believes this resolves the opposition between philosophers of monism and dualism – both are true because they are the true experiences of two different kinds of people. Some of us have minds distinct from the objects or phenomena we perceive, some of us do not. We are born as dualist or monist. Most immaterialists identify with dualism, and materialists with monism; philosophers who are monist are often immaterialists, dualists are materialists – but the range of ideas is very great.
What do scientists think about consciousness today? Some progress is being made, vindicating Bertrand Russell’s prediction that science would impinge on philosophy. First they say the obvious: an individual can be in many different states of consciousness, for example from being awake to asleep, from being anaesthetised to being in a persistent vegetative state. They have used methods such as functional magnetic resonance imaging to show that different states of consciousness are associated with different levels of neural activity in different parts of the brain.
It is difficult to avoid the inference that consciousness requires and is caused by specific kinds of biochemical and biophysical neural activity which can detected and measured.
Second, sadly, many people suffer from genetic disorders that affect their mental capacity to various degrees and their brains show different kinds of neural activity. It is likely that many of them experience consciousness in ways that differ from the norm.
Thirdly, we may wonder about the kind of consciousness experienced by unusually talented people, for example while concert pianists are playing complex sonatas and concertos faultlessly often at great speed without the music – are they conscious of what they are doing moment by moment? Great tennis players make shots which they cannot have time to think about.
Fourthly, we can surmise that a newborn child is not conscious in the same way as an adult: consciousness is an activity of the brain that changes with the development of the individual while maturing and, of course, while ageing, for example with dementia.
Finally, it is certain that human and animal consciousness evolved, probably slowly. Consciousness is certainly a complex trait and so it is likely to be have been affected by changes in many genes over evolutionary time.
In summary, there is a consensus among scientists that consciousness depends on scientifically measurable activities in the human brain and varies with the activity of the brain. Berman may well say that these are all minor variations on the underlying dichotomy between monist and dualist, but this remains to be investigated, by scientists.
He ends his book with an astonishing hypothesis about the consequences of the hybridisation that took place between two sub-species of humans, Homo sapiens and Homo neanderthalensis, 70,000 to 25,000 years ago in Europe and/or Asia. He is correct there is excellent genetic evidence for the hybridisation – modern Eurasians have about 2-3 per cent Neanderthal DNA. The “pure” Neanderthals went extinct but the hybrids [modern Eurasians], who ended up with predominantly H. sapiens genes, survived and prospered. Berman says the initial and continued success of our hybrid ancestors was due to the emergence of language during this early period, and that this was a result of hybridisation of H. sapiens [who may have brought an ability to vocalise] with the Neanderthals [who may have contributed a capacity for the core dualistic experience – dualism].
This is fantastic speculation about language. In spite of what Berman says there is no consensus among scientists that humans acquired language in this time frame of 70,000 to 25,000 years ago. We have little or no idea when recognisably “modern” linguistic ability appeared fully formed in the human lineage; but following Darwin and modern genetic theory about complex traits, it is likely that the process took hundreds of thousands if not millions of years and probably predated the separation between Neanderthals and Homo sapiens.
I am worried that Berman has relied far too heavily on Sapiens by Yuval Harari (2004), a highly successful example of what is called “infotainment”, full of titillating ideas for which there is little or no evidence. Harari was educated as an historian and has no expertise in any relevant science – one reviewer described Sapiens as having made “no serious contribution to knowledge”. However, if Berman is right that language developed in a few tens of thousands of years at the time our ancestors mated with Neanderthals, he will take his place alongside Democritus who put forward the atomic theory more than 2,000 years before there was any evidence for it.
One last comment. Neuroscientists might decide to repeat Berman's questionnaire on a large scale, perhaps modifying it. If they find they can make a reliable distinction between monists and dualists, they will surely want to study them in much more detail, including studying them for differences in brain activity and genes. They would be testing Berman's daring hypothesis that there are two fundamentally different kinds of human minds; they might find the differences are ultimately explicable in material terms and go some way to explaining consciousness. That would be something.
David McConnell is Fellow Emeritus at the Smurfit Institute of Genetics, Trinity College
