Soul, Mind & Body


Dualism: the view that there are two different types of existence: mental and physical.

Substance dualism: Descartes’ version of dualism that the two different types of existence are two different substances, e.g. mental (characterised by thinking) and physical (characterised by extension). A substance is a type of existence which cannot be broken down into anything further.

Monism: the view that there is one kind of existence.

Materialism: the view that the one kind of existence is physical substance.

Plato’s dualism

Plato believed the body was like a prison for the soul, trapping it in this world of appearances. He thought our souls came from the world of forms and had a vague memory of the forms.

Look up charioteer analogy

The argument from recollection/innate concepts

Plato argues for the forms and the soul, based on the fact that we seem to have a concept of perfect beauty and justice in our minds by which we judge what things or situations are more or less beautiful/just than others.

P1: We have a concept of perfect justice and beauty.
P2: We have never experienced perfect instances of such things.
C1: therefore we must have a soul which gained those concepts from the world of the forms before we were born.

We are born with a dim recollection of the forms because our immortal soul observes them before being reincarnated. Anamnesis is the process of re-remembering these forms through a posteriori sense experience.

Justice and beauty are subjective. Beauty and morality are arguably in the eye of the beholder. They seem like matters of opinion, not fact. It seems to be culture that determines and conditions what a person finds beautiful or just and as a result, views on what is beautiful or just change over time and differ cross-culturally. So, there is no objective perfect beauty or justice.

Maths is not subjective. Plato also makes an argument from recollection about maths, specifically geometry. It is much harder to argue that geometry is subjective so this is a stronger version of the argument from recollection. In The Meno Plato tells the story of how Socrates attempts to prove that a slave boy who had no education could nonetheless be prompted by a series of questions and some shapes drawn in the sand, to figure out how to solve a geometry question. The conclusion is that humans have innate knowledge of geometric truths gained from when our souls existed in the world of forms.

Mathematical knowledge could come from experience. The slave boy may not have had any mathematical training, but he had seen shapes of objects in his life – thereby gaining concepts of shape and geometry from experience.

Plato’s cycle of opposites argument

P1: Every change from one state to another must involve a cycle of opposites. E.g. something becoming ‘smaller’ must be cycling away from ‘bigger’. A quality which has an opposite comes into being from its opposite.

P2: This cycling involves two opposite processes; e.g. increasing and decreasing. If these processes were not equally balanced, everything would be eternally getting bigger and bigger or smaller and smaller.

P3: Something dying is cycling away from the process of coming into life. Therefore, something coming into life must be cycling away from the process of death.

P4: This process must be balanced otherwise there would be only dead things or no dead things.

C1: There must be a soul which is cycling between life and death

Cycle of opposites criticism: Arguably ‘life’ and ‘death’ are not objective qualities but just descriptions of different arrangements of atoms. Objectively they cannot be opposites, therefore.

Arguably the universe is getting bigger and bigger, and has been doing so since the big bang, not for eternity. So Plato’s argument fails because he could not have been aware of the discoveries of modern physics.

Aristotle: Plato’s theory lacks empirical validity

Aristotle thought the success of his theory of the four causes showed that Plato’s theory of forms was an unnecessary hypothesis, because it has no explanatory power regarding our experience. Plato’s forms are unchanging, but therefore cannot explain the change we experience in the world. This is like an early version of Ockham’s razor and is a general principle in empiricist epistemology: we should not believe explanations that are unnecessarily complicated, such as a world of forms, when we have a simpler theory that works. Aristotle concluded that the forms are “nonsense, and even if they do exist, they are wholly irrelevant”. Plato’s theory of forms lack empirical validity.

Aristotle does not reject the idea of form itself, but only the separation of form from things. On Aristotle’s view, a thing’s form or formal cause is its essence; its defining quality that makes it what it is. This also led Aristotle to reject Plato’s mind-body dualism, since the form of a human (rational thought) cannot be separated from their body.

Aristotle’s materialism

Aristotle rejected the idea of the world of forms as lacking empirical validity, thus he also rejected the idea of some non-physical soul which could have come from such a world. Nonetheless, Aristotle still believes in the soul, but as the form of the physical body.

Form means essence, which is a thing’s defining characteristic. For a chair, its defining characteristic would be its shape, a shape that can be sat on. However, the essence of a human is not merely its shape. Aristotle claimed the defining feature of a human being is the ability to reason. Aristotle claimed that the soul was the formal cause of the body. He made an analogy with a stamp imprint in some wax. The imprint of the stamp has no actual positive existence separable from the wax, yet it nonetheless gives form to the wax. This is the relationship between the body and the soul for Aristotle.

Formal causation is unscientific. Bacon argued that form was a metaphysical matter, not an empirical one. He gave the illustration of the ‘whiteness’ of snow and explained how science could investigate how snow results from air and water, but this only tells us about its efficient cause, not the form of ‘whiteness’, which is thus not a scientific matter.

Modern science goes further in its rejection of formal causation. The idea that colour is a ‘form’ of an object is now much better understood to be a matter of the activity of particles like atoms and photons.

For Aristotle, the form of a human is a rational soul, but most neuroscientists would claim that rationality reduces to brain processes. So what Aristotle thought of as ‘form’, actually reduces to material structure. There appears to be no room left in modern science for formal or final causation.

Science cannot currently explain how consciousness or reason reduces to material brain processes. The brain is so complicated and while some of it is understood a bit, processes like reason and consciousness have not even begun to be understood. So modern science cannot yet justifiably dismiss Aristotelian soul & form as the explanation of reason.

However, there is scientific evidence at least linking the brain to reason, since if the brain is damaged then reason and other mental faculties can be damaged too. Since there is so much about the brain we don’t understand, it’s more reasonable to think that mental faculties like reason are reducible to the material causation of brain processes in a way we don’t yet understand, rather than requiring some other type of physical explanation such as Aristotelian form since there is no evidence for that.

Descartes’ substance dualism

Descartes argued that the soul exists. He was a dualist which means he believed there are two substances (a substance is a fundamental type of existence which doesn’t depend on anything else) – mental and physical. The essence of mental substance is thinking, the essence of physical substance is extension.

Descartes’ indivisibility argument

Leibniz’ law is that identical things must share the same properties. The physical has the property of being divisible but the mental does not. Therefore, they are not identical, otherwise that one thing would have both the property of divisibility and indivisibility, which is incoherent.

The mental is divisible. The mind can be divided into perception, memory, emotions and so on. Freud proposed the Id, Ego and Superego. So, the mind and body share the same property of divisibility and thus could be identical.

Descartes responded that although the mind has these separate abilities or modes, that does not count as division of the mind because it is still the same mind that perceives, that remembers, that has emotions, experiences the animalistic desires of the Id and conditioned information of the Superego, and so on.

Divided hemispheres. There are phenomena which have been discovered by modern psychology which could suggest that actual divisions of the mind are possible, e.g. blindsight & separated brain hemispheres. The brain is split into two hemispheres which are only connected by a thin strand of neurons called the corpus collosum, which can sometimes be cut as a medical procedure to treat epilepsy. This has the bizarre effect of, some have argued, seeming to result in two separate ‘persons’ in the one body. The right hemisphere controls the left arm and the left hemisphere the right arm. Patients have been observed picking up some food with one arm and the other arm hitting it away. One case involved a patient who tried to hug his wife with one arm and push her away with the other. Whether this proves that consciousness has been divided is debatable but it at least casts doubt on Descartes’ notion that we have the full picture of what our mind actually is merely from how it seems to be to itself.

Not everything thought of as physical is divisible e.g. quarks. If some physical things are indivisible (quarks) then that shows that it’s not the case that all physical things are divisible. In that case, the mind could also be one of those things that are physical but not divisible.

The conceivability argument

We can conceive of the mind without the body, therefore it is possible for the mind to be separate from the body, therefore the mind is not identical to the body. This is because Identity entails the impossibility of separability. If I can conceive of the mind as non-extended then I can conceive of it as disembodied. If conceivability entails possibility, and I can conceive of a mind without a body (a disembodied mind) then that shows mind and body are separate. E.g. we cannot conceive of a triangle without 3 sides because it is truly identical with the property of having 3 sides.

P1 – I have a clear and distinct idea of myself as a thinking non-extended thing.
P2 – I have a clear and distinct idea of my body as a non-thinking extended thing.
P3 – what is conceivable is possible.
C1 – therefore the mind and body can possibly be separate, so they are not identical.

Masked man fallacy. Arguments based on conceivability are susceptible to the masked man fallacy. Imagine you heard about a masked man robbing a bank. You can conceive that it’s not your father, but if it really was your father then it’s impossible for it to not be your father, yet that was what you conceived. Therefore, we can conceive of the impossible. In that case, something’s being conceivable does not mean that it is possible.

The masked man fallacy shows that ignorance can lead to conceivability of impossibility. However, there is no analogous ignorance when it comes to our knowledge of our own mind. In that case there will be no conceivability of impossibility borne of ignorance.

Conceivability is based on ignorance: Descartes assumes that the way the mind appears to the mind is how the mind actually is. Neuroscience shows us that we are only aware of a tiny amount of brain processing. It seems then that what we experience is not the whole picture of what the mind actually is. In that case, it’s possible that the mind is divisible or that it does have extension.

The interaction problem

This is a criticism of dualism. If dualism is correct and the mind and body are separate fundamental types of existence, how is it possible for them to interact? It seems that a mental desire to move a hand causes the bodily movement of the hand moving, and when the hand touches something hot it causes the mental feeling of heat. This requires non-physical mental substance to causally affect and interact with physical substance, but it’s not clear how that would be possible.

Princess Elizabeth of Bohemia argued that only physical things can interact with other physical things. She says interaction is when one thing pushes against another. A non-physical thing cannot do this. Therefore, if the mind is non-physical it cannot interact with the physical. However, it appears that the mental can cause the physical e.g my desire to touch a water bottle causes my arm to move and touch it. Therefore, dualism is false.

Descartes defence: Descartes tried to solve the interaction problem by suggesting that the mind and body interact at the pineal gland.

Counter-defence: There is no evidence or argument given in support of Descartes’ claim. He wrongly thought only humans had a pineal gland, but biologists later proved that false. More importantly, Descartes is saying where he thinks the mind and body interact, but the interaction problem doesn’t question where but how. Descartes is not providing an answer.

Empirical problems for interaction. Furthermore, Physicists say that the universe is ‘causally closed’ because of the second law of thermodynamics that energy can be neither created nor destroyed – only transferred from one state to another. This means that energy cannot come from outside the physical universe and affect things within it. However that seems to be how substance dualism would have to work since the mental is supposedly outside the physical universe. Therefore substance dualism is false.

Gilbert Ryle & the category mistake

Ryle critiqued dualism, especially Descartes’ substance dualism:

“I shall often speak of it, with deliberate abusiveness, as “the dogma of the Ghost in the Machine“. I hope to prove that it is entirely false, and false not in detail but in principle. It is not merely an assemblage of particular mistakes. It is one big mistake and a mistake of a special kind. It is, namely, a category mistake.”

Ryle claimed Descartes was making a category mistake. Descartes says that physical things are extended, divisible and are non-thinking. He then argues that since the mind is non-extended, indivisible and thinking, it cannot be a physical thing and must therefore be a non-physical thing. Ryle argues that conclusion does not follow. Just because the mind is not a physical thing, that doesn’t mean it must be a non-physical thing. There could be another option – the mind might not be a ‘thing’ at all, of any type!

To illustrate why, Ryle told the story of someone being shown around a university. After they had been shown the various buildings, they then asked ‘but where is the university?’ They had mistakenly thought the university belonged to the category of ‘buildings’, rather than in the category of ‘a collection of buildings’. It’s as if they asked ‘what is the taste of blue?’

Ryle argues that the language we use to describe the mind confuses us about the logical category it belongs to. We use the word ‘state’ and ‘process’ to describe physical things, but also use those words to describe mental terms. Since only physical ‘things’ can be in physical states or undergo physical processes, we thereby confuse ourselves into thinking that the mind must also be a ‘thing’ as it can be in mental states or undergo mental processes. Descartes, on the basis of that confusion, finds himself unable to locate a physical ‘thing’ that could be the mind and so wrongly concludes that it must be a non-physical thing – mental substance.

Descartes mistakenly puts the mind into the category of ‘things’ when really the mind is in the category of sets of dispositions.

Ryle illustrates this with the example of the “brittleness” of glass, which is the disposition of the glass to shatter upon impact. Is the brittleness of the glass a ‘thing’? Where is the brittleness of the glass? Does it have extension, can it be divided? Clearly such questions don’t make sense. Dispositions are not ‘things’. But of course, we wouldn’t be tempted to think of the brittleness of glass as being some kind of non-physical thing, so nor should Descartes’ arguments tempt us to think of the mind as a non-physical thing either! So, for Ryle, who thinks of the mind as a disposition, it makes no sense to treat the mind as belonging to the category of ‘things’ or ‘substances’.

Criticism of Ryle: However, is the mind really a set of dispositions? Doesn’t it ‘feel like’ something to have a mind? Reducing the mind to a set of dispositions doesn’t seem to satisfactorily capture nor explain the fact that conscious awareness at least ‘feels’ like it ‘exists’ in some sense. It’s difficult to characterise that sense, but it seems overly reductionist and minimal to regard it merely as existing as dispositions to behaviours. Ryle was a philosophical behaviourist which is a controversial version of materialism.

Defence of Ryle: Ryle might be wrong that the mind is a set of dispositions, but he’s arguably still right to point out Descartes’ assumption that because the mind is not a physical thing, the only option is for it to be a non-physical thing. Who knows what other options there could be, aside from dispositions. Descartes’ conclusion at the very least requires much more justification than he gives.


Dawkins is a scientist and materialist. He argues that our current scientific view of what we are is that we are merely material physical beings composed of DNA. That’s all there is scientific evidence for, therefore we shouldn’t believe in anything supernatural such as a soul.

Dawkins argued there are two types of soul – one valid the other invalid. Soul 1 is the view that the soul is a real thing separate from our body, which Dawkins rejects due to lack of evidence. Soul 2 is a metaphorical idea of the soul, as a metaphor for the deep part of our mind and personality where the essence of our humanity is. For example, someone who doesn’t believe in a soul might still say “I felt that in my soul” or “Hitler was a soulless person”. They are just using the term ‘soul’ metaphorically for our deep important human feelings, not for some non-physical part of (soul 1). Dawkins thinks that everything about us, including our minds and consciousness, is nothing more than biological processes in our body and brain.

David Chalmers can be used to criticise Dawkins. Chalmers distinguishes between the ‘easy problem of consciousness’, which means figuring out which brain process is responsible for which mental process such as memory, perception or emotion, and the ‘hard problem of consciousness’, which is what brain process is responsible for consciousness itself. Chalmers points out that neuroscience has made progress as solving the easy problems of consciousness but has not come close to solving the hard problem. Chalmers recognizes the progress of neuroscience at solving the easy problem of consciousness but thinks that its failure thus far to make any significant progress at solving the hard problem suggests that explaining consciousness will require discovery of something new which is radically different to anything we currently understand. This could be a dualist mental property, but Chalmers admits it could also be a materialist physical property or thing we’ve not yet discovered. Our physical universe, once fully understood, could be just as far beyond our current conception as we are beyond Aristotle’s.

Defence of Dawkins: There are many things science cannot currently make much or any progress on, such as dark matter. This doesn’t give us grounds for supposing something non-physical might exist. We still have no evidence that anything non-physical exists.

Neuroscience is a young science and the brain is so incredibly complicated that it’s no surprise that no progress has been made on the hard problem of consciousness. That cannot be evidence for the possibility of science not being able to understand it because of it being a non-physical thing. In fact, since we know that there is so much about the physical structure of the brain that we don’t understand, arguably that should be a case for expecting the explanation of consciousness to be found once we gain more scientific understanding of the physical brain.