Is Physicalism true? (A brief guide)

In this guide, we will discuss “Is Physicalism true?” and a few important aspects of physicalism philosophy. For the purpose of this article, we will try to argue why we believe physicalism is not doesn’t do any justice to the complexity of mental properties when reducing it to physical effects.  

Is Physicalism true?

According to the Stanford Encyclopedia of Philosophy, “Some philosophers (e.g. Davidson 1970) have thought of physicalism as a conceptual or necessary truth, if it is true at all. But most have thought of it as contingent, a truth about our world which might have been otherwise. The statement of physicalism encoded in (1) allows a way in which this might be so.” Two more arguments could support that physicalism is true but we will try to explain according to theorists and philosophers why it is considered false.

In contrast, seeing the world through the eyes of non-physicalists leaves the door open to the idea of whether or not the real world conforms to those conditions ‘as a matter of fact’. Physicalists argue that the world is entirely physical and for many contemporary philosophers this seems to be the ultimate truth. But others refuse to believe this is true because they doubt that mental and psychological processes are physical or can be reduced to a physical aspect. 

Understanding the world and everything in it as the interaction of electrons, protons and neutron through certain forces, gravity and electromagnetism seem to give us the sense that there is a piece missing, with more questions than answers. Let’s talk about what is physicalism and how physicalism explains consciousness and mental processes. 

What is Physicalism?

As indicated by William Seager from The University of Toronto:

“Physicalism is a monistic metaphysics: it claims that there is only one basic kind of reality and it is physical in nature. The phrase ‘kind of reality’ is vague and ungainly; in the past materialist philosophers would have said there was only one kind of substance, or even more straightforwardly, only one substance: material, or physical, substance. But our grip on the idea that substance is the appropriate concept by which to describe basic reality has weakened. The rough idea remains clear enough: at bottom, everything is physical.”

With this approach to what physicalism means we are left wondering how does those who support physicalism explain the mental processes and how the mind is conceived as to have physical properties. But do we believe everything is physical? Not really and even more so if we don’t only interpret this from a scientific perspective. 

Physicalism and consciousness

One of the most powerful arguments for this view, and many physicalists would agree, is known as the causal argument and it is the thought that unless the mind were physical, it couldn’t have effects in the physical world. Descartes was one of the most famous anti-physicalists that argued that there were two separate realms, the mental and the physical. But other philosophers criticized his point of view arguing how if they are so different, they can affect each other. 

Going back to our main argument, we would have to assume that mental events have physical properties or effects. In general, we believe that feelings, thoughts and decisions are mental events that have effects on the body and thereby, have the power to influence the physical world.

For our second premise, physical effects can be fully accounted by a prior history of physical causes. For instance, we could talk about how neurons release neurochemicals to communicate with each other allowing me to transform this into thoughts. But some might argue that premise one and premise two would have been enough acting on its own. 

However, we would need to consider our third premise as the physical effects of mental causes aren’t all overdetermined and here we could be tempted to argue that mental causes are themselves out of the physical world.

Is Physicalism true? (A brief guide)

The knowledge argument

It is one of the most well-known arguments against physicalism and the most recognized version starts with Frank Jackson’s story about Mary. Mary is a brilliant neuroscientist who is a specialist in colour experience and since she is so smart, intelligent, etc., she knows everything there is to know about the brain and what goes on when a human being experiences colours.

Moreover, she knows all the science but she has been raised all her life in a black and white room so she has never experienced colours, only seen black and white so she has learned what she knows and the brain science watching everything through a black and white TV. 

Mary goes out into the world, being released from her black and white prison and she sees a red tomato for the first time. This would be the first time she experiences the red colour and the proponent of the arc the knowledge argument believes that at that point, Mary learns something new. However, let’s not forget she already knew all the brain science so the new fact she learns must be a fact that goes beyond what brain science could have taught her.

Subsequently, there has to be more to the experience she has with colour than the kind physical-brain science facts and so physicalism must be false.   

Parts of the knowledge argument

Now that we have put ourselves in context, let’s talk about the two parts from the knowledge argument. The first one says that physical knowledge is not sufficient or enough for phenomenal knowledge, also called knowledge intuition. 

Moreover, the second argument says that the knowledge intuition entails the falsity of physicalism and even though many others have tried to depict the concept of knowledge intuition, it wasn’t until Jackson that we could consider this to be the best attempt. But additionally, he provides reasons for inferring physicalism is not true.

Just as indicated by Torin Alter from The University of Alabama, The Mary case divides the knowledge intuition into three claims:

  • The complete-knowledge claim: before leaving the room, Mary knows everything physical.
  • The learning claim: upon leaving, she learns something.
  • The non-deducibility claim: if the complete-knowledge claim and the learning claim are true, then what Mary learns when she leaves the room cannot be a priori deduced (deduced by reason alone, without empirical investigation) from the complete physical truth.

Subsequently, the Mary case seems to give out powerful reasons to argue that physicalism can’t be true since physicalists don’t seem to be able to explain the lack of relevant phenomenal knowledge and how if she knows what it is like to see colour, she acquires this knowledge only when she leaves the room. 

Why is this blog about ‘Is Physicalism true’ Important?

As we have discussed on ‘Is physicalism true?’ we believe many arguments are supporting the falsity of physicalism. We understand that physicalists claim that there is only one basic kind of reality and it is physical in nature and how philosophers have indicated there is only one substance, material or physical. But we don’t agree with their perspective and perception of the world even if they don’t really deny the existence of items of a biological, or psychological nature.

However, as we have discussed with the case of Mary and the knowledge argument, knowledge intuition entails the falsity of physicalism and even though many others have tried to depict the concept of knowledge intuition, it wasn’t until Jackson that we could consider this to be the best attempt. Providing reasons for inferring physicalism is not true.

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Frequently Asked Questions (FAQs) about Is Physicalism true?

Why is Physicalism true?

Some philosophers argue that physicalism can’t be true because it would not account or allow us to have new experiences or learn new things. For physicalists, experiences would be reduced to brain activity (reductive materialism) but experiences are independent of brain activity. There are mental and physical components that appear to be different entities. 

Are Physicalism and materialism the same thing?

The terms Physicalism and materialism have been used interchangeably for quite some time by some philosophers meaning they are the same thing. However, we can say that according to the theoretical premises that explain each, they are not the same thing but they are closely related. To better understand the difference, materialism says that reality is composed of material things or ‘hard stuff’ and physicalism indicates that all that exists is not necessarily matter or is not observable like energy or physical fields. 

Who invented Physicalism?

It is said that the term ‘physicalism’ was first coined by the Austrian philosopher Otto Neurath back in the early 20th Century. The term physicalism is said to be closely related to the concept of Materialism since it is said to have evolved from the physical sciences incorporating the notions of physicality as matter. However, physicalism is also considered a variety of Naturalism, which is the belief that nature is all that exists and all supernatural things do not exist. 

What are Physicalism and dualism?

Physicalism explains the nature of being through a ‘one substance’ perspective as opposed to Dualism which talks about two substances. Physicalism argues that everything that exists in the real world (even mental processes), can be explained or described through the language of physics while dualism is the theory that indicates that mental and the physical (mind-body or mind-brain). For dualists, both substances are independent but they seem to affect each other.

What is non-reductive materialism?

Non-reductive materialists indicate that mental processes are ontologically part of the material world but mental properties can exist without being reduced to physical properties. For instance, a non-reductive materialist would argue that mental properties can never be explained in terms of neural states. Another example would be the inability to explain biological causes in purely physical and chemical terms. 


Alter, T. (n.d.) The Knowledge Argument Against Physicalism. Retrieved from “Physicalism” “Consciousness & Physicalism”