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Introduction

I first read Arthur Koestler's The Ghost in the Machine in the early 1970s, and Gilbert Ryle's The Concept of Mind a few years later, along with the Discourse and Meditations by René Descartes.  Descartes famously describes a mind-body ('Cartesian') dualism, which subsequent generations found to be a significant problem - how can a non-material mind affect or be affected by a material body?  Koestler popularizes the work of Ryle (and others) in promoting a materialist and behaviourist solution to the problem.

All of these thinkers (and many others) talk about the body - or the brain - as a machine, and the mind - or soul - as an immaterial something which acts on the body and brain.  I have never been satisfied with this description, and over the years many conversations have circled around it.

For a long time, it has seemed obvious to me that a missing piece of the picture - a very significant missing part of the picture - is a recognition that your body is not a machine.  Or, more precisely, your body is not just a machine: your body is a living organism.  And life is not the same as non-life.  It now seems to me that these fairly obvious observations are central to resolving Decartes' dilemma.

Life and Non-life

In the discussions about Cartesian Dualism, we usually talk about human life, reason and rationality, minds and souls, but the fundamental distinction we should be making is not between human and non-human: it is between life and non-life.

Non-living things are just that - things, objects.  Some objects are fairly stable, like rocks; other objects are changing in various ways - meteorites crashing into a planet, or minerals dissolving into water, or uranium ore slowly decaying.  All the things which are true of non-living things are also true of living things - they are subject to gravity and to chemical reactions.  But living creatures also behave in other ways: they typically eat and grow, and they all reproduce.  Every living creature has desires (fundamentally: survival, safety and success), and every living creature acts with purpose; usually, this is not conscious purpose (a bacterium is not conscious in any meaningful sense), but the action is purposeful, done to achieve a certain aim.  A universe without life is a universe without desires and without purpose.

People sometimes argue about whether a virus is alive: the answer depends on your precise definition of 'alive'.  But if you divide the world into life and non-life, it is clear that a virus belongs to the 'life' part.  A virus can exist in a universe with life, but it cannot exist in a universe without life.

Life Messes with Boundaries

We can investigate a rock, or a molecule, or an atom.  We know, more or less, what we are talking about, and what we learn will apply to similar examples in other places and at other times.  Every electron behaves exactly like every other electron - if we learn about one, we learn about all of them.  If we meet intelligent aliens, they will know the same physics and chemistry as us.

But we cannot investigate a living organism in the same way, and when we try to do it, we find that a different living organism, even of the same kind, may act quite differently.  Living creatures do not just exist; they interact with their environment, in ways which are often complex and always purposeful.

And the interaction of a living creature with its environment creates a blurred, fuzzy boundary between the creature and its environment.  Some of the gas in my lungs is in the process of becoming me, and some of it used to be me and is in the process of becoming not-me; some of the food in my gut is becoming me, and the stools in my intestine are in the process of becoming (or, perhaps, have already become) not-me.  Even more confusingly, my gut microbiome is clearly not-me from a genetic perspective, but it is clearly me from a functional perspective - I probably cannot live, and I certainly cannot be healthy without it.

So the distinction between me and not-me in purely physical terms is unclear and constantly changing.  And I live in a social and cultural context: if you want to understand who I am, you have to understand my language, beliefs, hopes and fears; you have to understand my family, friends, home, and country; you have to understand my history and habits; you have to understand my expectations and plans; you have to understand my hobbies, interests and skills; you have to understand the poems and books I have read and the groups I identify with.  We are social creatures: people who live alone have the TV and radio for company, or a dog or cat, or even a goldfish - you cannot understand me without understanding the people and people-substitutes I constantly interact with.  And, when you have understood me, you have learned very little about the person standing next to me.  Every living creature is, in a significant way, unique.

Machines, on the other hand, are clearly boundaried and may be mass-produced: apart from manufacturing errors, they are - and they are intended to be - identical. 

The Body is Not a Machine

The body acts like a complex machine, at least in part.  At a mechanical level, we understand how the muscles and skeleton work together to enable the body to move; at a biochemical level, we understand parts of how we gain energy from the food we eat.  But food is not fuel - at least, food is not just fuel, supplying the body with energy: much of the food we eat is ingested and becomes part of us.  So the body is a machine which builds itself, which is constantly building and rebuilding itself, which is constantly changing and adjusting to its environment, which is made up of small parts which each have all the information needed to create the whole, and which has both the desire and the capability to reproduce.  The body is a machine which can recognize the presence of objects which are not part of itself, and seek to destroy them, a machine where the difference between me and not-me is fundamental to its activity.

Living creatures interact with their environment.  Of course, non-living matter also interacts with its environment - but there's a difference.  Non-living matter always and only interacts with the environment as it exists, as it really is.  Living creatures interact with the environment as it is perceived to be, which can be quite different.  And living creatures also interact with the environment as they expect it to be - sometimes, as they hope or fear it will be.  But, whatever the details, living creatures interact with an environment which does not exist.  We plan, and act in the light of an anticipated future; we plant seeds so that, one day in the future, we will be able to use what we grow - but the future we plan for does not actually exist, you cannot touch, taste or measure it.

Machines have sensors, computers receive data as input from multiple sources: these are often claimed to be equivalent to the senses of living organisms.  When when we excperience anything, it is because the outside world has changed us.  Cells in our nose and mouth react to the chemicals in our food; when we touch an apple, we feel how our skin is moved, displaced by it; when we hear birdsong, the hairs in our ears vibrate; when we see a flower, the photons of light trigger a biochemical cascade in the photoreceptor cells in the eye.  A living organism being changed by the outside world is completely different from a machine receiving a data input.

In other words, the body is a machine almost completely unlike every machine we have ever built.  The body is a living, growing organism which, while sharing various obvious characteristics with non-living matter, has many complex characteristics which are fundamentally different from non-living matter. 

We talk about a sense of self, as an attribute of intelligence.  But the ability to distinguish between me and not-me is built into every living creature: the sense of self is only the intellectual aspect of a functioning reality we all share - even an amoeba does not attempt to eat itself.  We are discovering an increasing number of medical conditions which trace back to auto-immune problems - which are caused because one part of us does not recognize another part as self.  The more we learn, the more important it becomes to distinguish correctly between me and not-me.

And, to state the obvious, no machine we build has (or can have) a sense of self: they are comprised of levers and springs, of wires and transistors and resistors, every one of which is replaceable by an equivalent part.  An Artificial Intelligence may 'know' about the neural network which generates its responses, but the integrated circuits in that network do not belong to the AI in the same sense that the cells in my brain or liver belong to me.  You may be able to trace an integrated circuit back to the company which designed and manufactured it, but there is no DNA equivalent: you cannot trace it back to the computer or car you took it from.  

In Summary

In short, a materialist solution to Cartesian Dualism does not work because the body, the living organism, is not only material; the other side of the coin is that the problem of Cartesian Dualism itself, how a non-material mind interacts with a material body, is only a problem if you believe the body is only material.  Granted, something which is only a machine, a mechanical body-like thing, would have no place for a mind.  But a living organism is almost completely unlike a machine, and many of the fundamental aspects of the living organism are not material.  All living organisms have desires and intentions, even if they are not expressed in intellectual form.  The desire of an organism to reproduce is not physical, although the expression of that desire is.  No living creature is purely physical, and we fool ourselves when we talk as if that was the case.