Substance Dualism (what is)

In this guide, we will discuss “Substance Dualism”. We will briefly mention what substance dualism is, the problem of interaction where the basic question is,  “if the mind and body are two distinct and separate entities and how they interact?” Additionally, we will mention what property dualism is and how it differs from substance dualism. Finally, we will take a look at another problem related to substance dualism and some additional considerations around this philosophy.

What is Substance Dualism?

Substance dualism is considered a variant of Dualism where there are two concepts in this notion, substance and dualism of these substances. When we talk about substance, we also talk about the properties of this substance but for some, it is more than the collection of the properties. Subsequently, the mind is not considered only as a collection of thoughts but an immaterial substance over and above immaterial states. 

As mentioned by Britannica, “dualism is committed to the view that mind constitutes a fundamentally different substance, one whose functioning cannot be entirely explained by reference to physical phenomena alone. Descartes went so far as to claim (in accordance with contemporary church doctrine) that this substance was an immortal soul that survived the dissolution of the body.”    

This ultimately means that if someone died, the body would cease to exist (i.e. decay) but the soul will remain since it is believed to be independent of the body. We can see that this premise has been adopted by Christianity, many years ago. In this tradition, it is firmly believed that we have a soul and our soul is somehow connected to our mind. 

However, one of the many questions that arise from this philosophy of the mind is ‘Are the mind and body distinct entities or is the mind merely whatever is happening inside our brain?’ This has to do with the problem of interaction that many philosophers have attempted to answer through the different theories of consciousness.

The concept of substance

As indicated by Paul Richard Blum from the Rebus Community, “Descartes’ philosophy of mind was a response to the erosion of the traditional Aristotelian concept of substance after the Middle Ages. According to the Aristotelian view, any substance is composed of matter that is determined by the form that is its essence. So every living thing is a body conjoined with its soul (namely, what makes it alive as such or such thing).”

However, in his ‘Principles of Philosophy’, Descartes’ interpretation of ‘substance’ seems to point to its independent existence and applies only to God (defined as perfect and not dependent on anything). But in the real and material world, we learn about substances due to their physical properties so many would believe he was a proponent of physicalism when attempting to explain the mental processes (i.e. perceptions, feelings) in physical terms. 

The problem of interaction

Substance dualism can have many problems and one of the main problems being the problem of interaction. We could mention here the premise ‘if the mind and body are two distinct and separate entities’, How do they interact?

Let’s see an example, if my mind says that it wants to move (i.e. jogging), how is it that it causes the body to move? How does the non-physical mental substance interact and cause the movement of a physical and material substance such as the body? There seem to be several approaches to this objection that the substance dualists but we won’t necessarily talk in-depth about their perspective. 

However, according to Descartes our mind and body interacted through the pineal gland. But this explanation about the interaction can be seen as a fatal flaw for dualism but at the same time, we could see and understand how there could be a distinction between mind and body or how they could exist independently from each other but with the ability to interact or affect the other. If this is the case, other theorists and philosophers would have in fact, turned to property dualism to give out a more ‘accurate’ answer.

Property dualism

Property dualism theorists believe that ultimately, the reality is made of just one substance unlike substance dualists argue. This only substance is believed to be the physical but what substance dualists define as the mind is in fact non-physical properties of the physical properties. This means that our thoughts, ideas and consciousness are non-physical properties and they are not referred to as a different substance. The mental can in fact be reduced to physical properties according to property dualism. 

In other words, since the mental is a non-physical product of the physical brain, the neurons and the synapses allow the mental properties and so here is where the mind-body problem is. Subsequently, the world is just made up of the physical and the mind can be reduced to the physical. But the phenomena of mental properties is just down to the arrangement of the physical if matter is arranged in a precise and exact way mental properties will appear.

Let’s take the example of heat from Thomas Nagel and Saul Kripke into consideration. We feel the sensation of heat as a non-physical property but this is reduced to kinetic molecular energy. Since heat is the non-physical sensation we get to feel coming from the physical molecular motion, it could be useful to understand that mental ideas normally come about through physical changes. 

Another example is the pain you could feel because you cut your arm or hit yourself in the toe and we could indicate that there seems to be a difference between mind and body. However, let’s take a look at the concept of substance.

The problem of other Minds

To refute dualism, theorists propose the problem of how we can get to know other minds. If the mind is not publicly observable, the existence of other people’s minds different from our own must be inferred and ascertained as true as a result of the behaviour of another person or living organism. However, some may argue that this is not a convincing argument and must not be taken as reliable. 

Subsequently, behaviourists, mind-brain identity theorists and functionalists are some of the many rival theorists that use the problem of other minds to support their theory’s arguments. For instance, in the case of behaviourists, when they define mental states they don’t mean that mental states are behavioural, so it seems to be controversial in the sense that some argue it tends to reduce mentality to behavioural, brain or functional states.

In contrast, unlike other approaches, materialist theories seem to be less vulnerable to this type of problem when compared to dualist theories but they seem to deal with other problems. 

Why is this blog about Substance Dualism important?

As we have discussed on this blog about substance dualism, we have to remember that philosophers who defend this point of view argue that the mind and the body are distinct types of substances (mental and physical substances) with different properties but yet they seem to affect one another. On the other hand, we have property dualism, which argues that there is only one kind of substance (the brain) which has different kinds of properties.

Many problems arise from the substance dualism perspective that seems to be answered through property dualism and even other theories, pointing out the flaws that come from the arguments that make the substance dualism theory. However, we could determine that one of the pros related to substance dualism seems to be that it respects the difference there is between the mental and the physical. 

Please feel free to leave any comments or thoughts about the content of this article!

Frequently Asked Questions (FAQs) about Substance Dualism

What is substance dualism?

Substance dualism or cartesian dualism has been made famous by René Descartes, who argued that there are two kinds of substances: mental and physical. This philosophy indicates that the mental can exist independent from the body, and the body can’t think. Substance dualists believe the two substances are independent of each other but they still interact or have an effect even if it is not clear how because they have nothing in common (different properties).

What is the difference between dualism and substance dualism?

Dualism claims that the mind, which is different from the physical human frame, is linked and will end with our death. Unlike dualism, substance dualism claims that the mind/soul is a separate entity than the physical substance that will live on, past the deterioration of the physical body. This is mainly an idea adopted by Christianity where the soul is an immaterial substance that gets to live independently from the body but it is not clear how this gets to happen since the link is not established yet.

Who created substance dualism?

Descartes was a substance dualist and he stated that there were two kinds of substance: physical and mental substances. The first, which has the characteristic or property of being spatially extended and the mind has the essential property of ‘thought’.

What is the problem with substance dualism?

The problem with substance dualism can be expressed in the following argument:

– If substance dualism is true, then we cannot know the mental states of others.

– We do, on at least some occasions, know the mental state of others.

– Therefore, substance dualism is false.

What is an example of dualism?

We can think about examples of epistemological dualism as being and thought or subject and object. Additionally, examples of metaphysical dualism are God and the world, body and mind or matter and spirit.

References “Dualism” “Philosophy of mind” “Substance vs Property Dualism (What is the difference?)”

Clef, S. (n.d.) Dualism and Mind. Internet Encyclopedia of Philosophy. Ohio Wesleyan University. Retrieved from

Blum, P.R. Chapter 1. Substance Dualism in Descartes. Retrieved from

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