In this post, I will bring my exploration of the realm of the mind to a close.

What is the best explanation of the form and nature of our conscious experiences? In my last three posts, I have considered various features of our experience that, I believe, do not and cannot have any complete explanation in physical reality.

Given the nature of consciousness and conscious experiences, our ability to reason, and our awareness of the self, I think materialism is just as incomplete of a philosophy as idealism. Just as idealism fails to explain our experiences of the physical realm, materialism fails to explain how we can have experiences at all. The evidence overwhelmingly demonstrates that both the physical and the mental exist.

Substance Dualism

This leaves me with the philosophy of dualism. As I explained in an earlier post, there are two major forms of dualism: property dualism and substance dualism. And I think substance dualism is the more reasonable position of the two. Briefly, here are my reasons why:

  • If there are two radically different kinds of properties, mental and physical, it makes sense for there to be two different kinds of entities that have those properties.
  • Property dualism has mental experiences but no experiencers. In my view, it cannot account for the first-person perspective of our experience without becoming substance dualism in disguise.
  • Substance dualism provides the most natural account of personal identity over time, while property dualism implies that the self-awareness I discussed in this post is illusory.
  • Property dualism has no active causation and no agents. It implies that free will and rational thought are just illusions.
  • Only substance dualism accords with certain other aspects of the worldview that I believe to be best explanation of all of reality.

To elaborate on these points further: first, property dualism already introduces a kind of dualism in the entities, and not just the properties, that exist. There are entities or systems with only physical properties, and entities or systems with both physical and mental properties.

However, most forms of property dualism only assign mental properties to certain complex systems – but there is no strictly physical principle which can single out just which systems these are. The systems themselves effectively become new entities, bearing properties that are not derived from the physical properties of the matter making up the systems.

This seems to me to be nearly the same as a form of substance dualism that has mental entities bearing the mental properties, and standing in an embodiment relation with the complex physical systems. In fact, I think substance dualism is a simpler and more straightforward way of framing the way mental phenomena are related to the physical realm.

To evade this objection, property dualism would have to postulate something like “atoms of qualia” that could be associated with less complex physical subsystems, and that somehow combine to build up the mental phenomena that we experience. But I do not see any way this could work.

Second, property dualism is usually joined to a position called epiphenomenalism, which is that the mental properties of a system are only “along for the ride” and do not affect the system’s physical behaviour. Property dualism is generally thought to imply epiphenomenalism because the only entities that exist are physical, and physical entities are subject only to the passive causation described by the laws of physics.

Now, there could be new causal powers and liabilities among the mental properties that are acquired by certain complex physical systems. But I do not think the forms of mental causation that are available to property dualism could be active causation: active causation is essentially performed by a first-person perspective, and that leads us back to property dualism’s problem with incorporating first-person perspectives.

So mental causation would still just be passive, subject to natural laws operating in the mental realm. There simply is no such entity, in property dualism, that is capable of acting of its own accord and for its own reasons. This makes free will and rational deliberation into an illusion, which I think is a fatal flaw for any philosophical position. Property dualism, if true, would eliminate the existence of rational thought – and that makes it a self-defeating belief.

Third, substance dualism is implied by another aspect of what I believe to be the most coherent and comprehensive worldview. Specifically, substance dualism is implied by the existence of God and Christian doctrines about the afterlife.

I will be exploring why I believe what I believe about God and Christianity in future posts. Suffice to say that because of the implications of God’s existence, whatever independent reasons I have for believing in God are also reasons for believing in substance dualism.

Embodied Minds

So for the reasons I have given above, and in the last few posts, I believe that reality contains mental entities in addition to physical entities: the mental realm is as real as the physical realm. In particular, the self that I am aware of through introspection is an immaterial entity: a mental substance. (Recall that this is the philosophical meaning of substance, not implying that the self is made of any kind of material-like stuff.)

Since my self is immaterial and non-physical, but it is a real entity, we have to call it something. So we may call this self a mind, or a spirit, or a soul. Since it is a conscious first-person perspective with the capacity to be self-aware, to reason, and to exercise free will, we may call my self a person.

(As an aside, I believe the correct definition of a person is along these lines: a person is a member of a natural kind, the normal members of which have the capacities for consciousness, self-awareness, rationality, free will, and moral accountability. This is because my intuitions say that, for example, human beings who are in permanent comas, or who have been mentally disabled since birth, are still persons with intrinsic value even if they do not exhibit the capacities that we usually associate with personhood.)

My intuitions about my self lead me to believe that minds (or spirits, or souls) are metaphysically simple entities: they do not have separable parts. My self cannot be divided up into different pieces capable of independent existence. Though we can divide minds conceptually (for example, considering emotions as distinct from the faculty of the will), they cannot be divided up in reality. The “part” of my mind that feels emotions and the “part” that makes decisions cannot be ripped apart into distinct entities.

Minds, according to my view, are mental atoms (in the original sense of the word “atom,” before we learned that physical atoms could in fact be divided). Though they have highly complex properties (such as thoughts about abstract mathematics), they are not composed of more simple entities. This is one of the things that makes the mental realm so different from the physical realm.

Finally, though they are distinct, non-physical entities, the minds we are most familiar with (our own) are intimately related to certain physical systems, namely, our bodies. We are embodied minds. (In fact, it may be more accurate to characterize ourselves as body-mind composites.) So my position is a form of interactionist substance dualism. The body can causally affect the mind, and the mind can causally affect the body.

We experience both of these directions of causation all the time. My mind is constantly receiving sensations from my body, and I exert my free will to use my body to perform various actions throughout the day. Of course, through science we have discovered that this interaction is mediated via the brain – and our minds and brains are so intimately related that our physical brain states significantly impact our mental states.

This is not really an astonishing revelation of modern science. People have known for millennia that there are things we can do to our bodies (drinking certain fermented beverages, for example) that may alter how our minds function. Modern science has just shown us how this can be done in more detail, and perhaps that this can be done to a greater extent than we once imagined.

But my arguments in the last three posts point to the fact that, despite their close connection, our mental states are not the same thing as our brain states. Influence is not identity; our mental states are influenced by our brain states, but their essential features show they are not identical to our brain states.

So what are we to make of the mind’s dependence on the brain? My view is something like this: the immaterial mind uses the brain as an instrument of thought. The mind uses the brain to think, experience, and act within the world, in the same way that a pianist uses a piano to play music. This is the view that, to me, makes the most sense of what we know about reality.

Why our minds and bodies are so connected, and how they got that way, are deep and important questions – but they are questions for another time.

Objections to Substance Dualism

Now that I have articulated my position of substance dualism, I will consider the reasons weighing against it.

Interaction Problem

The first argument against dualism is the interaction problem. How can these two vastly different realms of reality, the physical and the mental, interact with each other as the dualist says? The objection is that the dualist posits an inexplicable causal interaction relationship between mind and body.

This objection presupposes that it is unreasonable to believe that something causes an effect if we cannot explain how that thing causes the effect. But this is just false, so the objection fails. You do not need to know anything about the physiological mechanisms of intoxication to reasonably believe that drinking alcohol will get you drunk. Likewise, our experience provides sufficient justification for belief in the causal interaction between the mind and the body. An explanatory mechanism for the causal interaction is unnecessary – though of course, it would be an advance in understanding.

Fortunately then, it is also false that the causal interaction between mind and body is totally inexplicable. Here is a plausible explanation: it is just among the basic causal powers and liabilities of the immaterial mind to be able to affect the brain in certain ways, and to be affected by the brain in certain ways.

The postulation of basic causal powers is a reasonable and natural move, given that the mind is a basic indivisible entity with other complex properties. Without a similar move, physicists could never explain how fundamental particles and fields interact with each other, for example. Under this view, the mind and the brain just interact directly with no intervening mechanism. And the fact that the mind and brain are so different does not really seem to be relevant to this.

A related objection is that the mind and body cannot interact, because such interaction would violate the laws of physics, and these kind of violations have never been observed. But I think this objection misunderstands what the laws of physics are.

The laws of physics are descriptions of the causal relationships within a physical system. They say what will happen within a physical system, absent any external influences that have not been accounted for. But a mental cause is just such an influence, especially since the laws of physics have been formulated based on experiments outside of the complex environment of human brains. The claim that the laws of physics are totally inviolable, even by non-physical causes, is simply unjustified.

In any case, is there any reason to suspect that such violations due to mental activity would be detectable? The mind could interact with the body by means of extremely small effects, which then propagate up to the observable level according to the usual physical laws. Plausibly, the brain is a chaotic system in the mathematical sense, so that very small differences in initial conditions can lead to very large differences in outcomes. Only the initial tiny input would be against the laws of physics, and it seems unlikely that we could measure such a thing in the environment of a living brain.

The opponent of dualism might complain that this makes dualism into an unfalsifiable hypothesis. That would be a valid complaint if dualism were a scientific hypothesis. But that is not, strictly speaking, what it is. Dualism is a philosophical position motivated by our first-person experience. So this complaint only has force if you believe that science is the only valid source of knowledge – which is just a belief that is unjustified and self-refuting.

Problem of Other Minds

The second objection consists of two related arguments called the problem of other minds and the problem of many minds. These problems ask, how do we know that the other people we interact with have minds? And how do we know that they only have one each? If consciousness is only first-person accessible, how do we know that anyone else has it?

This, of course, is still a problem for the opponent of dualism, but it is supposedly more of a problem for the dualist, because substance dualism posits entities (minds) that can only be known through introspection. So the belief in other minds is apparently only justified by the weakest possible inductive inference: a sample of one (your own mind).

Of course, this objection is easily overcome. Because the belief that other people have minds, and only one each, is most plausibly seen not as an inductive inference, but an abductive inference: an inference to the best explanation. And the best explanation of the behaviour that we observe from others is that everyone has a mind just as we find ourselves to have.

This is on top of the fact that the belief in other minds could easily be taken as a properly basic belief: a belief naturally formed in the context of our interpersonal experience, and therefore possessing inherent justification. So without evidence that other people do not have minds, it is reasonable to believe they do.

(As an aside, this response means we can also infer that, most likely, many kinds of animals also have conscious experiences and minds. However, since there is less similarity between ourselves and animals than there is between ourselves and other humans, the inference is not as strong. So animals likely have different kinds of minds than we do, if they have them. Specifically, there is no conclusive evidence that animals have the rational and volitional capacities that we do, so while they may have minds, it would be a stretch to assume that they are persons.)

Strangeness Objection

A third objection that I have seen is that substance dualism is just too strange. What are these mysterious immaterial entities and subjective phenomena? They are just too far removed from our experience to be believable!

Obviously, this is a pretty weak objection. The mind is only strange and mysterious if you assume that physical reality is all there is, or that all reality has to resemble physical reality. Without that assumption, the mind is not strange at all. Really, there is nothing we are more familiar with than the mind. We just spend more time looking outwards, at the things around us, than we do looking inwards, examining the mind itself.

Occam’s Razor

The fourth argument that I have found against substance dualism is Occam’s razor. This is the principle stating that, when we are formulating hypotheses in an inference to the best explanation, we should not postulate anything more than necessary to explain the evidence. So according to the objection, dualism is less preferable because it postulates two kinds of entities, physical and mental, while materialism only postulates one.

However, this objection only works if materialism and dualism have the same explanatory power. But my whole argument in the last few posts has been that this is not the case: the existence of the mental realm is necessary to explain our subjective experience; the physical realm is insufficient. So Occam’s razor does not cut against dualism.

Here is another way to put this. A materialist might say something to the effect that dualists need (and lack) substantial justification to postulate consciousness as a fundamental constituent of reality in addition to the physical properties of mass, charge, and spacetime. But that objection misconstrues the problem, because consciousness is not something postulated to explain the phenomena we experience. Rather, it is one of the phenomena that needs to be explained.

Optimistic Scientism

This brings us to the fifth and final objection against dualism, the argument from science.

Some people might claim that biology and neuroscience show that consciousness can be explained without the hypothesis of an immaterial mind. But I think an honest look at what we know shows that this is not the case.

We know much about the processes going on inside the brain, and there is absolutely no explanation for how those processes might give rise to first-person subjective experience. In fact, it is worse than that. There is absolutely no explanation for how any conceivable physical process might give rise to first-person subjective experience, even in principle.

The argument from science is that, even in spite of this difficulty, we should continue to expect that science will be able to explain consciousness by a natural, physical mechanism. Science, the objector says, has been all about demystifying the universe, explaining everything by the laws of physics. Dualism goes against this program, threatening to undo the progress of science and spread a primitive, anti-scientific worldview.

This, I think, is really nothing more than an optimistic scientism.

Science has certainly been successful in explaining many natural phenomena, but it is not the only source of knowledge. And it is simply false that, as some materialists put it, everything we have investigated so far has turned out to have a natural explanation via the laws of physics. Consciousness itself is the foremost counterexample. (The origin of the universe and its fine-tuning for life are two other problems that have proven quite difficult in this regard, I might add.)

Mental phenomena differ in very significant ways from other natural phenomena that we observe. Their first-person perspective and their subjective experiential quality are fundamentally unlike any natural phenomena that has ever been explained by science. So an inductive inference or reasoning by analogy that says, “Science has explained these other things, so it will be able to explain consciousness too,” simply is not justified.

Because of the privileged first-person access of conscious experience, the most that biology and neuroscience will be able to show is that there are certain correlations between our mental states and the physical states of our brains. But this kind of correlation does not conflict with the position of substance dualism – far from it, if we believe that minds use brains as instruments to think.

Furthermore, the justification for substance dualism does not come from its ability to explain our physical brain states, but from its explanatory power in the realm of our subjective experience, and from direct introspective awareness. So scientific advances that increase our understanding of neurology do not affect the justification for dualism. To do so, the scientific theory would have to explain how and why we have conscious experience – but as I have argued, the physical realm has no mechanism that can do this.

In the end, the study of science is actually impossible if dualism is false. Science depends on our ability to reason, and if materialism is true, reason is an illusion. So far from being an anti-scientific worldview, it is dualism rather than materialism that is the worldview most compatible with science. The real scientific worldview is the one that includes the possibility of rational scientists.


Weighing the arguments for and against the position of dualism, I can only conclude that the physical world is not all there is. There are very strong reasons to believe that the laws of physics cannot possibly explain the existence of our conscious experience. Rather, the very nature of our experience reveals that there is an immaterial component to our existence.

The mind, or soul, or spirit, is real. This belief is supported by many religious teachings, but I hope by now I have shown that it can be arrived at independently of such considerations. Dualism is not a relic of more primitive ages, but a rational and justified belief – and a more complete explanation of reality, compared to philosophical materialism.

This seems to me to be a very important thing to know about ourselves, something that gets to the very core of what we are. As I said early on in my blog, what we believe affects the way that we live. Recognizing our spiritual nature is a significant part of understanding reality, ourselves, and how we should live in it.

There are many questions that I have not endeavoured to answer here, of course. Can the mind or soul survive apart from the body? The radical dependence of the mind on the brain does not make this appear likely from a scientific perspective – though there are other important considerations, and many people find unembodied existence to be intuitively possible. Or, when does the immaterial part of each of us come into existence? The first-person privileged access of mental phenomena makes that a very difficult question to investigate.

But I think that questions like these, and others, are ones that we should investigate. By gaining a better and more complete understanding of ourselves, we can better understand the best way to live in our world.

With that, I am almost done the second major section of my blog. There is one more topic in this section that I want to cover. So in the post after next, I will be writing about certain things of value – the true, the good, and the beautiful.

(First though, since I have covered so much ground, my next post will be a summary of my conclusions, thus far, about the nature of reality.)

Free Will and Rationality

In my last two posts I have presented reasons to believe that the mental realm exists and is distinct from the physical realm, from the nature of our conscious experience. In this post, I will present further reasons for this position, and in my next, I will examine the reasons against it.


Teleology, like intentionality, is a property of certain mental phenomena not shared by any physical phenomena. While intentionality is the feature of being “of” something, teleology is the feature of being “for” something.

Some of our mental states are intentions of certain purposes that we have. And other mental states appear to be more than just experiences, but are acts of will, such as the act of purposefully thinking about some topic, or the act of moving one’s body (or at least willing to do so). Such acts are done for certain purposes or reasons. These mental states have intrinsic teleology.

Just as they have no intrinsic intentionality, physical states of affairs have no intrinsic teleology. A stone that happened to break in such a way that it has a sharp edge does not have any intrinsic purpose. It merely is. But it can have derived purpose if some agent intends to use it to cut something. Or even better, if it was broken to have a sharp edge for that purpose by the agent in the first place.

Things that are designed or used have derived teleology from the agent that designed or used them. But no physical system can design or use something else. Purely physical systems have no purposes and undertake no actions. Rather, they are passively subject to the cause-and-effect relations described by scientific laws.

Since I experience mental states with intrinsic teleology, I therefore have reason to believe that there is more to reality than just the physical.

Free Will

Much of the debate about the reality of mental states with intrinsic teleology revolves around the question of free will. Do we really have free will, or is it merely an illusion? And if free will exists, is it compatible with everything being explained in terms of passive causation? Or does it require active causation that cannot be reduced to the operation of natural laws?

I believe our experience of being agents who act in reality gives us powerful justification for properly basic belief in the existence of free will. We perform both mental and physical actions of our own volition, all the time. Our mental states appear to cause other mental states, as well as physical ones. So we should believe in free will unless we have powerful evidence to the contrary.

Further to that, I believe our intuitive concept of free will requires irreducible active causation. My reasons for believing this are as follows.

As a philosophical theory, compatibilism is the thesis that free will is compatible with our actions and mental states being completely explained by passive, external causes. Incompatibilism, on the other hand, is the thesis that free will is not so compatible. According to incompatibilism, a freely willed action or mental state requires an irreducibly active, internal cause in order to be completely explained.

(Note: the debate between compatibilism and incompatibilism is often framed in terms of being about whether free will is compatible with actions being determined, but I think the question is better framed the way I have put it here. If my actions are completely explained by physical events in my brain, then I don’t think it matters whether those events are ultimately deterministic or indeterministic.)

Incompatibilism, combined with the belief that free will actually does exist, may also be known as libertarianism (no relation to the political viewpoint), or the belief in libertarian free will. The philosophical debate between compatibilism and incompatibilism/libertarianism is extensive, but I will try to cover it briefly.

There are three main points of disagreement about what is required for free will:

  • The control condition: a free action must be controlled by the agent.
  • The ability condition: the agent must have the ability to choose to perform the action or not.
  • The rationality condition: the choice to perform the action or not must be made by the agent, for reasons that the agent may have, and not just be the result of random forces.

I believe the incompatibilist position fulfills all three of these conditions better than the compatibilist position, fitting our intuitive concept of free will.


The control condition is the defining point of disagreement, revolving around what ultimately causes free actions. Incompatibilism holds that for an action to be free, it must in some way have originated with and been caused by the agent performing that action. This requires irreducible active causation: if the action could be completely explained by passive causes, then it would just be part of a causal chain that stretched back to before the agent even existed. For an action to be free, it must be determined at least in part by the agent himself, as an originating cause initiating a chain of events.

Compatibilism instead holds that an action can be free even though it is completely explained or determined by causes external to the agent, as long as the causal chain leading up to that action “runs through” the agent in the appropriate way. For example, a compatibilist might say that an action is free as long as it is appropriately caused by the agent’s desires and beliefs.

To me, compatibilism seems insufficient to fulfill the control condition. If my actions are completely explained, in the end, by external forces beyond my control, then they are not my actions. They are mere happenings that have been thrust upon me. If that is the case, we are just passive systems subject to the laws of physics. We are not really free to determine what we will: compatibilist free will is illusory.


The ability condition says, essentially, that free actions must not be forced: the agent must be able to do the action, but he must also be able to refrain from that action. Incompatibilism holds that this is a real dual ability. According to incompatibilism, the agent must have both the ability to perform the action and the ability to refrain, in reality and in the exact same circumstances. All that determines whether or not the agent performs the action is whether or not he freely exercises his causal power.

This is not to deny that a person’s circumstances and character may strongly influence his decision to act or refrain from acting. For example, a mother’s love may strongly influence her decision to run into a burning building to save her child.

Now, perhaps she still had a choice to go into the building or not, in which case there is no conflict with the ability condition. If she was so compelled that she had no choice, then an incompatibilist might say that her action was not free in a first-order sense, but that it was free in a second-order sense, because it was caused by circumstances and aspects of her character that were a result of first-order free actions.

I think this makes sense. The most important condition for free will is that the action originates from the agent and is not completely determined by external causes (the control condition). In many cases, but not all, this implies that the agent can both perform the action or refrain from doing so (the ability condition).

Compatibilism, meanwhile, holds that the ability condition can be satisfied if the ability to refrain from the action is merely hypothetical. For example, the agent would have refrained from the action if his character or circumstances had been different. But on the compatibilist picture, given the agent’s actual circumstances, he could not have done differently than he actually did.

This also seems insufficient to be properly called free will. The process of rationally deliberating between two options presupposes that both options are open to us. Unless incompatibilism is true, and in at least some cases we really do have the dual ability to act or refrain from acting, all deliberation is irrational. It merely serves as part of a chain of events, outside our control, that gives us the illusion of making a decision.


Finally, the rationality condition says that free decisions have to be made for reasons, not just random forces. Some compatibilists would say that an action cannot be free unless is actually is determined (in other words, free will is not just compatible with but actually requires determinism): since a free action has to be appropriately caused by the agent’s desires for acting.

The incompatibilist, however, views our desires not as the causes of our actions, but as goals or purposes for which our actions are done. Desires and reasons are teleological rather than causal in nature. And I think this also better accords with an intuitive concept of free will. The passive causation of the laws of physics contain no reference to intrinsic teleology. Because of this, there is a huge difficulty in compatibilism of finding a clear principle for distinguishing between causes that are rational reasons for a free action, and causes that make an action not free.

Incompatibilism, on the other hand, allows for active causation by mental entities, with direct reference to intrinsic teleology of mental states. Reasons are clearly distinguished from causes, and can be evaluated. So I believe incompatibilism also satisfies the rationality condition better than compatibilism.


As a last remark on reasons for incompatibilism over compatibilism, there are important moral intuitions that support the incompatibilist side of the free will debate on each of the above three points. (As I have said before, I think moral intuitions are also a valid source of properly basic beliefs, a contention I will defend further in a future post.) They are as follows:

  • If what we do is ultimately determined by forces outside of our control, then we cannot be morally responsible for any of our actions. But we are morally responsible for some of our actions. So compatibilism is false.
  • To be morally obligated to do something in a certain situation, we actually have to be able to do it in that situation. (We are not morally obligated to jump after someone who fell off a cliff to save them by flying like Superman: there is nothing we could do in that circumstance.) But sometimes we fail to do things we are morally obligated to do. So the dual ability presumed by incompatibilism is true, and the merely hypothetical alternate ability of compatibilism is false.
  • Moral reasons for actions seem to be better accounted for by the intrinsic teleology allowed in the incompatibilist approach.

These are further reasons to believe that incompatibilism is the correct conception of what free will really is.


So I find that there are strong reasons in favour of incompatibilism: free will requires irreducible active causation and intrinsic teleology. And according to the principle of critical trust, our experience of having free will is a strong reason to believe that free will exists. So this is another way in which our experience supports not just dualism, but substance dualism: since physical entities are passively subject to the fundamental laws of physics, any entity capable of active causation must be non-physical.

Are there comparable reasons in favour of compatibilism? When I search for the answer to this question, I do not think that there are. It seems to me that the usual reason people believe in compatibilism is that they believe in determinism (or more generally, they believe that our actions can be completely explained without reference to our own agency). Then they try to reconcile their experience of free will to this belief by trying to find a satisfactory compatibilist explanation – since they do not want to accept what would be the more obvious conclusion from determinism: that free will is just an illusion.

But what reason is there to believe that determinism, or the more general condition that everything can be explained in terms of passive causation, is true? The main reason just seems to be philosophical materialism, the belief that everything is physical and completely explained by physical laws. (Or some form of property dualism holding that mental properties supervene on the physical properties, without adding any kind of irreducible mental causation.)

I’ll look at reasons for rejecting substance dualism and accepting materialism (or property dualism) in my next post. But since my experience of having free will, and what seems to me to be the most natural conception of what that means, is itself an argument for substance dualism, it cannot be undercut by taking a compatibilist position when the main reason for that position is a belief in materialism. That would be arguing in a circle.

So my experience of having free will, and mental states with intrinsic teleology, adds to the force of my justification for believing in substance dualism. And unless an adequate account of compatibilist free will can be found – and I have not seen any that plausibly explain the experience of free will that I have – rejecting substance dualism means rejecting the existence of free will.

The Existence of Reason

My final reason for believing in the reality of the mental realm is the existence of reason itself.

Our ability to reason is the foundation of almost all of our knowledge. Without it, we could never form a cohesive worldview out of our many and disparate experiences. We could never acquire any knowledge about the world from science. We could never even rise above the responses of our basic instincts.

Because of this, any worldview that is inconsistent with the existence of reason is self-defeating. If your worldview implies that all of our thinking is ultimately irrational, it undercuts all reason you have to believe in it.

My argument now is that philosophical materialism is self-defeating in this way: it cannot explain the existence of reason, or rationality. Under materialism, there is no room for a self with intentional and teleological mental states, with the free will to choose one belief over another on the basis of a rational argument. Under materialism, there is no such thing as a rational thought.

In order for us to be able to use deductive reasoning, a number of things must be true:

  • We must have mental states with intentionality, specifically directed towards the propositional content of thoughts, so that we understand what we are thinking.
  • We must apprehend the laws of logic that are used in a deductive argument, and understand how to use them.
  • We must be able to accept the conclusion of an argument for the reason that we perceive how it logically follows from the premises.
  • Because the perception of the logical relationship between the premises and the conclusion is not instantaneous, we must endure through time to apprehend the complete argument and accept the conclusion.

The first and second requirements mean that intrinsic intentionality, and the qualia associated with experiencing such intentionality, must be real phenomena. In fact, it requires a particularly complex form of intentionality: understanding the meaning of statements or assertions, and understanding not only the meaning of the laws of logic, but that and how we can apply them. As I have already argued, intentionality and qualia cannot be reduced to the physical realm.

The third requirement means that there has to be a certain relationship between the mental state of considering the premises of an argument, and the mental state of accepting its conclusion. Specifically, for belief in the conclusion to be rationally justified, the agent must accept the conclusion because of the perceived logical relationship between the conclusion and the premises.

The “because” in the last paragraph is a teleological “because.” It is a reason, a purpose for which the agent performs the mental act of accepting a belief. This requires the existence of intrinsic teleology, and it requires the active causation of a mental state by an agent. In other words, rationality requires free will – which means if reason exists, substance dualism is true.

To expand on that point further: if someone’s mental state of accepting a belief can be wholly explained by a chain of passive causes – for instance, if all mental states could be wholly explained by the fundamental constituents of matter operating according to the laws of physics, with no reference to intrinsic intentionality or teleology – it seems highly questionable to me to think that the belief is a product of rational thought.

If I arrived at my beliefs because I was determined to do so by the causal forces of the universe, operating in causal chains stretching back to before I was even born, then I didn’t really accept my beliefs for rational reasons, even if I thought I did. Especially if physical states are all that exist, it is hard to see how the meaning of my beliefs could have any relevance to the causal chain.

And since truth is bound up in meaning, if I am caused to accept my beliefs in this way, then my beliefs have very little to do with the truth. Any true beliefs I hold are just by happenstance, since the forces causing my beliefs are indifferent to truth and rationality.

So for any of our thoughts to be rational, for us to be justified in thinking that any of our beliefs our true, active causation must be a reality. We must be able to cause a certain kind of mental state within ourselves, not because we are caused to do so, but because we have a reason to do so. We must be able to freely choose to accept a belief, without external causes determining that we accept it.

“Actions are rationally assessable only if the actions are free. The reason for the connection is this: rationality must be able to make a difference. Rationality is only possible when there is a genuine choice between various rational and irrational courses of action… If the act is completely determined then rationality can make no difference. It doesn’t even come into play.” – John Searle

And so, we must be the kind of beings that can act as uncaused causes for purposes of our own. But no merely physical entity or system is this kind of being. Physical systems are only passively subject to the causal forces described by the laws of nature.

The fourth requirement means that we have to endure through time to be able to reason. But as I argued in an earlier post, it is unlikely that we can find a meaningful principle derived from the fundamental laws of physics that would allow us to identify a merely physical entity as a self that endures through time. This means that our physical bodies cannot serve as the subject of an enduring first-person perspective. So if we are able to reason, we must be more than our physical bodies.

The existence of reason, therefore, has powerful implications. Rational thought requires that there is more to reality than the merely physical, because of the features of intentionality and teleology that are bound up in it. We cannot deny that we are able to think rationally; to do so would undermine almost the entirety of our knowledge, along with any justification for taking that position in the first place.

So we have to affirm that reason exists. And our experience of thinking rationally gives us good reason to do so. But this means that the mental realm, and mental entities inhabiting it, exist.

In my next post, I will bring all these considerations together and briefly elaborate on what I think is their most reasonable explanation: that we are embodied minds. Then I will consider the major objections to this position.

Qualia and Intentionality

Last post, I said that mental phenomena have a number of traits that I think are necessarily non-physical, properties that no physical system has:

  • They are experienced by a first-person perspective, a subject.
  • They have an irreducible subjective quality, a “what is it like to experience this.”
  • Some mental states have an intrinsic intentionality, a “what is this experience about.”
  • Some mental states have an intrinsic teleology, a goal, purpose, or “what this is for.”

In that post I examined the implications of mental phenomena being essentially experienced by a first-person perspective. In this post, I will look at two further properties of mental states: their essential subjective quality, and their intrinsic intentionality.

Subjective Quality

Mental states have an essential property not shared by any physical system: their subjective, qualitative character. Every mental phenomenon has a certain character that defines it, a “what is it like to experience this” property. The most essential thing about the mental phenomenon of pain, for example, is that it hurts.

Something similar can be said about all other mental states, from vivid sensations like seeing the colour red, to mere thoughts like believing that Ottawa is the capital of Canada. (Thoughts, it seems to me, are a kind of experience, just as sensations are. They simply have a different subjective quality, are perhaps less vivid and more complex, and are often actively thought rather than just passively perceived.)

Philosophers have a name for these “what is it like” properties, these varied, essential, qualitative characters of mental phenomena. They call these features qualia.

Here is a thought experiment meant to illustrate the reality of qualia. Suppose there is a scientist who is completely colour-blind, and sees the world entirely in shades of white, grey, and black. Nonetheless, she becomes the world’s leading expert on the study of colour vision. She comes to know every fact there is to know about the physical process of seeing colour. But even with all that knowledge, there is something the colour-blind scientist does not know – she does not know what it is like to experience seeing colour.

Now, if the colour-blind scientist were to discover a treatment to restore colour vision, and then get the treatment herself, she would come to know something, the first-person experience of the subjective quality of colour, that she could never know from third-person study of the physical world alone.

The scientist, before her colour-blindness was treated, might have been able to point to certain measurements of brain states in patients who had normal vision, and say “this is what seeing colour looks like from the outside.” But that would get her no closer to knowing what colour is like. When it comes to mental phenomena, describing what they look like from the outside is really to not describe them at all. It is the subjective, experienced character of mental phenomena that is their essential nature. Any description that misses that misses the point.

The problem is that physics has no place for such subjective features: nothing about the behaviour or motion of the fundamental constituents of matter contains or entails properties like “the experience of redness.” The study of the natural world through science has played a significant role in supposedly reducing the secondary qualities of physical objects, such as their colour or warmth, to more fundamental physical properties, such as their reflectivity spectrum or thermal energy. But the subjective qualities of physical objects were never really removed. They were merely relocated.

An apple does not really have the property of being red; it just absorbs or reflects certain wavelengths of light, and our minds perceive the colour red from that sensory data. But the subjective quality, the appearance of red, still exists – it exists more obviously than the apple itself, since we directly experience it in our consciousness. Just as consciousness cannot be an illusion, or else there would be nothing to perceive the illusion, so the subjective qualities we perceive cannot be illusions, or there would be no illusion to be perceived.

So physics has not reduced qualia to physical properties – instead, it has confined qualia to the mental realm. And while it has showed that some qualia (such as sensations) are the ways that we experience certain physical properties, it certainly has not done this for all qualia (such as thoughts concerning complex mathematics). Showing that qualia and consciousness itself are merely the result of physics would require something else entirely.


What materialists usually appeal to, in their attempt to reduce consciousness to the physical realm, is the concept of emergence. Consciousness is said to be an emergent phenomenon that supervenes on the physical state of affairs. Something about the physical complexity of human and other animal brains allows a new level of phenomena to occur, and the physical system exhibits new behaviour that does not occur in less complex systems. Yet, supposedly, this new behaviour is fully explained by physics operating at the more fundamental level.

Consciousness, on this theory, is said to be like the property of being a liquid. Individual molecules of water are not liquid; but the liquid behaviour of water emerges from the behaviour of many individual water molecules taken in aggregate. In the same way, an individual neuron is not conscious, but consciousness is supposed to emerge from the behaviour of many interconnected neurons.

There are problems with this kind of analogy.

It is true that the behaviour of liquids emerges from the behaviour of many individual molecules. But it is also true that once you know the behaviour of all the individual molecules, you already know everything there is to know about the liquid itself. The location and motion of the molecules tells you about the location, motion, and temperature of the liquid; the intermolecular forces of the molecules tells you about the pressure, viscosity, and surface tension of the liquid. Giving the properties of the liquid at the macroscopic level is just useful as a summary statement.

Not only that, but given the description of the behaviour of all the individual molecules, you will know that the macroscopic description of the liquid has to be the way it is. The microscopic state of all the molecules making up a liquid necessarily implies the liquid’s macroscopic state.

But this necessary connection between the underlying system and the supervening phenomenon simply does not exist in the case of consciousness. In fact, there does not seem to be anything that could provide this necessary connection, even in principle. The properties of molecules include location and motion and energy that translate up to the higher level description in the liquid. But what properties of neurons and their connections translate into qualia? What are the building blocks that make up the experiential quality of redness or sadness?

If you know everything about the physical state of my brain and its neurons, you will still not know what I am experiencing unless I tell you, or you use some other inference that ultimately depends on first-person access to mental states. And there is nothing to suggest that the correlations between mental states and brain states had to turn out the way they did – the same qualia could have been attached to completely different brain states and structures, and nothing about the workings of physics would need to change.

Liquidity is just a structural property, a property defined by the structure and interrelations of the microscopic constituents of the liquid. Consciousness, on the other hand, is something completely new. Nothing about physics explains or necessitates its appearance, and there is no way to explain or derive it from the motion of the fundamental constituents of matter.

(The thought experiment that philosopher David Chalmers uses to illustrate this fact is the logical possibility of philosophical zombies – beings exactly like humans, but with no conscious experience. Indeed, a world populated by such philosophical zombies is exactly what we should expect, if materialism were true, since the fundamental laws of physics say nothing about the subjective qualities of conscious experience.)

So I think the emergence theory of consciousness is really nothing more than an unsupported postulate. There is no conceivable explanatory mechanism for consciousness from fundamental physics, either as we know it or as it is likely to be in the future. And it is absurd to suggest that a future theory of physics will include ad-hoc rules for associating conscious experiences with particular physical states. That kind of addition to physics, it seems to me, would just be another name for property dualism.

Based on this, I think it is reasonable to believe that conscious experiences are truly non-physical. The mental is not reducible to the physical; the mental realm is a fundamental part of reality.


Some (if not most) mental states are of or about other entities or states of affairs. For example, we can have a visual experience of a real tree in the forest, or we can merely envision a mental image of a tree, or we can consider certain facts about trees. This feature of “of”-ness or “about”-ness is known as intentionality, and it is another property of mental phenomena not shared by the physical.

We can know that intentionality is a real feature of mental phenomena because we directly perceive it, just like we directly perceive qualia. What we are thinking about is something we just immediately and directly know. And the fact that mere physical states of affairs do not have intentionality is a powerful intuition that comes, I think, from our recognition of the difference between the mental and the physical, and our experience of how we represent meaning.

To be more precise, physical states can have derived intentionality, but only mental states can have intrinsic intentionality: any “of”-ness or “about”-ness of a physical state is ultimately rooted in some mental state. For example, ink marks on a page are not intrinsically of or about anything, nor are sound waves in the air. Written or spoken words would not have any meaning in themselves without conscious minds who could use them to represent such meaning.

From what I can tell, the best attempt to reduce intentionality to the physical realm is to take the philosophical position of functionalism. Functionalism attempts to equate intentionality with the function of a system in terms of its inputs, outputs, and dispositions.

A software program is a good analogy here. A computer can be said to “know” how to calculate that 1+1=2 because it gives the appropriate output for the specified input, possibly modifying its internal state along the way. But of course, it doesn’t actually know anything. It is merely configured so that it is affected in the right way by the right input.

This is easily seen if the computer is actually made of dominos. You can build a “circuit board” of dominos that accepts certain inputs and produces certain outputs (if all goes well) so that the output corresponds to the result of adding two numbers. But the intentionality here is entirely derived; on a physical level there are dominos falling, and nothing more than that. If there were no conscious minds with intrinsic intentionality, using the inputs and output of the domino computer to represent numbers, there would be no intentionality in the system at all.

Increasing the complexity of the system would not change anything. Imagine that we made a domino computer of incredible complexity. And we made it much more reliable by making the dominos hinged to the ground so they only fell in the correct way, and we made it repeatable with a mechanism attached to each domino that put it back upright after it had fallen. Then, for all intents and purposes, we could make the domino computer do anything a normal electronic computer could do. (It would just be very slow.)

For example, we could make the domino computer run a simulation of a neural network. Say, a massive one mimicking all the myriad interconnections between the neurons of a human brain. But now, if materialism is true and there is nothing more than the physical realm, we would have something analogous in every respect to consciousness.

Sure, the domino computer might be the size of a city and take years to run a few seconds worth of simulation. But the size and time scale are not relevant to the functional aspects of the system’s behaviour. It would accept analogous inputs to those accepted by a human consciousness, and it would give analogous outputs. If functionalism and materialism were true, both the computer and the brain would have the feature of intrinsic intentionality – the domino computer would truly be thinking about things.

But it is obvious that the domino computer does not have any intrinsic intentionality. It does not have meaning of its own; we certainly do not expect that it would somehow develop its own conscious understanding of the inputs and outputs it was interacting with. But, if that is the case, what is different about the brain? The domino computer is nothing more than the mechanical reactions of waves of dominos falling over and standing up again; the brain is nothing more than the electrical and biochemical reactions of neurons.

Why should a system with the same functional behaviour, just made of a different material and operating on a different spatial and temporal scale, suddenly manifest intrinsic intentionality, or consciousness? Functionalism is a nice account of derived intentionality, but it does not do anything to explain our experience of knowing what we are thinking about, or of understanding the meaning of our thoughts.

(John Searle’s thought experiment of the Chinese room illustrates much the same thing as my domino computer example. Searle believes that consciousness is an emergent property of the brain, but from what I understand he also believes that there is no necessary connection between brain states and mental states. To me, Searle’s view just seems to be a version of property dualism.)

So the intrinsic intentionality of our thoughts simply cannot be reduced to software running on our brain. On functionalism, intentionality is nothing more than the system of inputs, outputs, and dispositions. But if that were true, then there would be no real intentionality at all: the intentionality of software is only derived, empty without some source of intrinsic intentionality to fill it. And since intentionality is a key component of meaning, there would be no meaning and no rational understanding.

The physical realm has no place for intentionality. But intentionality is a fundamental aspect of our subjective experience; it is an inescapable reality. We think about things, and we have experiences of things, and we understand the intentional meaning behind statements. But that means that the mental realm, the realm that carries intentionality, must be real.

I see no way for the physical realm to support features like qualia or intentionality, and I see no way to eliminate these features as illusory. So my experiences of these features convinces me that materialism is false, and some form of dualism is true. In my next post, I will look at one more feature of mental phenomena that no physical system can have – intrinsic teleology.


“I think, therefore I am.” – Rene Descartes

In my previous post I introduced the topic of this series: I am exploring whether our conscious experience gives us good reason to believe in the existence of a mental realm of reality, alongside the physical realm. I will begin by presenting the reasons why I think this is the case, and look at objections to this position in a future post.

I gave a working definition of “mental” in my last post, the precise content of which only really said that it is not physical and not abstract. Because I’ve defined it in this way, when I refer to what we would normally think of as “mental states” or “mental phenomena” (such as thoughts, conscious experience, and so on) I have to mean putatively mental: these are things that I am suggesting cannot be reduced to the physical realm. Strictly speaking, I can only call them mental, by my working definition, if my arguments for their non-physicality are successful.

But, since I don’t want to say “putatively” every time I mention such things, I will just call them mental, and let the context decide when that should be inserted implicitly.

Conscious Experiences

The (putative) mental world is vastly different from the physical world, with completely different characteristic properties. Physical entities are ultimately characterized by the states of their basic, microscopic constituents: the positions of particles, or the values of a field. Mental states, on the other hand, seem to be a completely different category. (There are no such things as “redness” particles or a “sadness” field.) And I think there is simply no way that our conscious experiences could be derived from basic physical entities, even in principle.

Mental states have at least two essential characteristics, and there are at least two other traits of some mental states that I think are necessarily non-physical:

  • They are experienced by a first-person perspective, a subject.
  • They have an irreducible subjective quality, a “what is it like to experience this.”
  • Some mental states have an intrinsic intentionality, a “what is this experience about.”
  • Some mental states have an intrinsic teleology, a goal, purpose, or “what this is for.”

None of these can be found in any system that is merely physical: none of them can be built up or derived from the motions of fundamental particles or quantum fields. The essence of this argument goes back at least 300 years, if not further:

“One is obliged to admit that perception and what depends upon it is inexplicable on mechanical principles, that is, by figures and motions. In imagining that there is a machine whose construction would enable it to think, to sense, and to have perception, one could conceive it enlarged while retaining the same proportions, so that one could enter into it, just like into a windmill. Supposing this, one should, when visiting within it, find only parts pushing one another, and never anything by which to explain a perception. Thus it is in the simple substance, and not in the composite or in the machine, that one must look for perception.” – Gottfried Leibniz

Updating the analogy to have a basis in electrochemical activity or any other physical principle, rather than in mechanics, makes no substantial change to Leibniz’s point.

Perhaps the most obvious difference between physical and mental is that the mental world is, in a sense, closer to us in how we know it. To illustrate this, consider that there is no logical contradiction in all of our experiences of the physical world being an illusion (however implausible that is). But conscious experience itself cannot be an illusion; that would be incoherent.

An illusion itself is a conscious experience, a mental state – it has a subject and a subjective quality. If consciousness were an illusion, the experiencer of the illusion would be unreal, and so no illusion would be experienced. And if conscious experience itself were an illusion, it would be unreal, and so there would be no illusion to experience at all.

Because of this, it seems to me that consciousness cannot possibly be explained away or eliminated. We can be wrong about what we experience, or wrong about what we remember, or wrong in what we believe. But we cannot possibly be wrong about the fact of having the experiences, memories, and beliefs that we are presently conscious of. It may be that all of our knowledge about the physical realm is fallible, but we can know at least some things about the mental realm incorrigibly.

First-Person Perspective

This stems directly from the fact that mental phenomena have a feature that no physical phenomena can possibly have: they are essentially experienced by a first-person perspective, and have first-person privileged access.

Physical states, such as the state of my brain with all of its neuron interconnections and electrochemical potentials and so on, do not have privileged access. They can potentially be measured with certain instruments and verified by anyone. So the physical realm is third-person accessible. But only I have access to my mental states; only I can know immediately and incorrigibly what I am experiencing in connection to the states of my brain that others are measuring.

Indeed, all ways of knowing about mental states ultimately reduce to first-person access. Any knowledge of someone else’s mental states comes either through:

  • the testimony of that person;
  • inference from their behaviour, based on observed correlations between behaviour and mental states; or
  • inference from their brain states, based on the observed correlations between brain states and mental states.

And observed correlations between mental states and either behaviour or brain states can only be generated by first-person access to our own mental states, or the first-person access of others via testimony.

This makes mental phenomena fundamentally unlike physical phenomena. Mental phenomena are only accessible to their subject, while physical phenomena are in principle accessible to anyone. This means that mental phenomena are non-physical.

But mental phenomena certainly occur. That is verified by every conscious experience we have, and it is a self-contradiction to try to explain away consciousness as an illusion. So the reality of the mental cannot be rationally denied. It follows that reality consists of more than just the physical realm.

Awareness of the Self

The first-person perspective of conscious experiences supports property dualism, but I believe it supports substance dualism even better. There must be entities who are the first-person subjects of conscious experiences, and no physical entity or system seems to fully capable of being the self that I am aware of.

When Descartes said “I think, therefore I am,” he was expressing a powerful and ubiquitous intuition that mental experiences imply the existence of an experiencer. It is an intuition that appears self-evident and necessarily true; and this is despite the difficulty in defining I.

(I do not believe this difficulty in any way undermines the intuition. Some concepts are primitive and cannot be further defined; this does not make them meaningless. If anything, it makes them more meaningful, because primitive concepts are what all other meanings are built out of.)

The entity that has my experiences is me, my self, I. There are a few other very common intuitions that many people have when considering the nature of the self. Here is how I express them:

  • I am a center of consciousness and volition.
  • I am capable of willing certain actions. My actions are not just things that happen; they are things that I do.
  • I am a single, unified entity. I am not divisible into separate components, and I do not exist in degrees. I either exist as a whole self, or not at all.
  • I endure through time as one and the same first-person perspective.
  • I have my experiences and memories, but I am not the same thing as my experiences and memories.
  • I have my body, and I act and experience reality through it, but I am not the same thing as merely my physical body. (More on this shortly.)

These are powerful intuitions, held by many people throughout history, though perhaps not always expressed exactly this way. The principle of critical trust entails that we should not abandon them without powerful evidence to the contrary.

One way to discover and clarify these intuitions is to consider various thought experiments revolving around personal identity. For example, if a mad scientist takes me and another person, records and erases our memories from our brains, and then imprints each person’s memories into the other’s brain, have we swapped bodies? Does the first-person perspective that is me travel along with my memories? Or do I stay with my brain, and just feel like I’ve swapped bodies, because I now have the other person’s memories?

For another classic example, if a Star-Trek style transporter deconstructs my body and creates a perfect replica of it at another location, do I really teleport? Or is the first-person perspective that is me destroyed along with my body, while a completely new experiencer is created, who only thinks he is me because he has a perfect replica of my body?

When I think about these kind of hypothetical scenarios, it seems to me that no amount of physical or psychological identity with another entity is sufficient to answer the question of whether that person is me. In any such scenario, I could say, “Yes, that is my body, or my brain, or my memory, but is it me?” And it would still be a valid question.

So why do I have these intuitions, and how can I explain them?

In considering all of this, I find that these intuitions are unified and explained by the fact that I am aware of my self. I am introspectively aware of more than just my experiences, thoughts, and emotions; I am aware of being an immaterial, indivisible, unified entity that endures through time. This awareness, like other experiences or intuitions, is a source of properly basic belief. In this case, it justifies belief in the existence of a certain mental entity – my self – that is distinct from my body, but that can causally interact with it.

The intuitions that I have referred to here are pre-philosophical and even pre-linguistic. That is, I would argue that they are not based on prior philosophical assumptions, nor are they derived from my worldview, nor are they a result of language shaping thought. Rather, they are among the basic beliefs that my worldview is based upon.

Some would claim that I only believe I have such an awareness because of learned cultural and religious beliefs about the soul. But that has things the wrong way around. Rather than being learned through religion, this basic awareness of the self is the reason that religious teachings about the soul are believable by the vast majority of people throughout history. It is where religious ideas about the soul originally came from.

Some philosophers claim to lack this basic awareness. For example, David Hume famously wrote that when he turned his gaze inwards, he found no self, only more experiences. (In a fitting response, Thomas Reid expressed astonishment that Hume’s Treatise on Human Nature had no author.) One reason for this may be that they are looking for the wrong kind of awareness. My awareness of my self is not a vivid sensation like the experience of the colour red. It is more like a second-order awareness that an experience of red is an experience of colour, or a non-vivid experience like understanding the meaning of a proposition. But it is a real awareness, nonetheless.

Another reason one’s basic awareness of the self might go unrecognized is due to a prior commitment to a philosophy like materialism. Experiences and intuitions are harder to discard than mere beliefs, but the worldview that we hold does influence how we interpret our experiences and intuitions. So if someone is convinced that the immaterial self does not exist, they may just interpret their awareness of it as not implying that they are distinct from their body.

So, I have a certain kind of experience, an awareness of my self, and because of that awareness I have the sorts of intuitions that I described above. These are not bizarre intuitions that no one else has; they have been shared by many people throughout history, and so are a well-established type of intuition. So I take my self-awareness as justification for a properly basic belief that I am not just a physical entity – in support of substance dualism.

Is this an unreasonable claim? That depends on the weight of the evidence against it, something I will look at a few posts down the road.

Mind and Body

The intuition that I am an indivisible entity deserves further elaboration. Consider that if my arm were amputated, it would simply cease to be a part of me; it is not the case that part of my self would be removed with it. To actually divide my self, a first-person perspective, into different parts is inconceivable. I have no idea what that would mean.

Which means, I believe, that I am not identical to my body. If my arm were amputated and replaced by a prosthetic, I would still be me. So my arm is not an essential part of me. (That does not mean it is not important. Please do not think that I would not care if my arm were amputated.) And I think we can extend that thought experiment to show that the same is true for any part of my body.

Prosthetic arms and legs have been around for a while. And considering that full-body transplants are getting close to the realm of technical feasibility, it isn’t hard to imagine a prosthetic body – replacing everything from the neck down. And that is only a few steps short of replacing everything except the brain.

It may be that we never get to that level of technology. But it seems within the realm of possibility, at least. But really then, just what is so special about the brain? It is nothing more than a network of neurons and their supporting structures. With a few more technological leaps, we can imagine that scientists could one day invent a prosthetic neuron, along with a fleet of medical nanobots capable of replacing a biological neuron with the artificial one.

It does not seem like replacing a single one of my neurons would make any more of a difference to what I am than replacing one of my arms (unless there is something special about neurons, something more than their physical properties). And the neuron replacement could conceivably be done without interrupting consciousness: the fleet of nanobots could install the artificial neuron while the biological one was still active, and then transfer function from one to the other with a speed at least as great as other electrochemical signalling processes.

Which means it is conceivable that my entire body could be prosthetically replaced, with the brain replacement done neuron-by-neuron to ensure its function and structure is preserved. And I would still perceive myself to be the same first-person perspective, with complete continuity of experiences. But if my body can be replaced while I am still me, then I cannot be the same as my body.

One other reason for thinking that I am not identical to my body is that I have the powerful experience of enduring through time and change – but it does not seem that my body can endure through time, unless there is some non-physical unifying principle that makes my body a distinct entity, compared to all the other physical systems that it might overlap with.

After all, if physics is all there is, then my body is just a collection of fundamental particles, or ripples in fundamental fields, or even just a pattern of momentary flashes in spacetime. The matter that makes up my body is in constant flux as atoms and molecules cycle through it. What, within physics, can say that my body or my brain is a single entity enduring through time? But if I endure through time and my body does not, then I am not the same as my body.

So, I believe that I am more than merely my physical body. Admittedly, I think property dualism might be able to explain the first-person perspective feature of mental phenomenon, and my intuitions regarding my awareness of my self. I will discuss why I think substance dualism explains things better, overall, in a later post. But regardless, I think the evidence of our first-person experience points strongly towards some form of dualism, and away from materialism.

To close this post, though, I want to make one note (which may seem slightly in contradiction with what I said earlier): I think there is a very important sense in which we can say that we are our bodies (even if we are more than our bodies). We act in the world and experience the world only through our bodies, and this makes them, in a way, an integral part of our being.

Any form of substance dualism consistent with our experience holds that we are embodied minds, not just minds disconnected from physical reality, and that our bodies are an important part of our human nature. So perhaps the best and most common-sense view is to say that we are body-mind composites as long as both of those aspects of our being exist.

So now I have looked at the first essential property of mental phenomena, their belonging to a first-person perspective. Next, I will look at their other non-physical characteristics.

The Realm of the Mind

A while ago now, I began my exploration of the nature of reality with a description of three different realms of reality that might exist. One of these was the abstract realm, inhabited by abstract objects such as numbers, propositions, and properties. (And I gave my reasons for thinking that the abstract realm does not actually exist.) Another was the physical realm, consisting of stars, planets, and biological beings in space and time. (And I gave my reasons for thinking that the physical realm does exist, and that we can learn about it through science.)

The remaining realm that our experience reveals to us is the mental realm. This is the realm that conscious experience itself resides in, with all the thoughts, concepts, mental images, and so on that go along with it. And it is the realm where the entities that have conscious experiences exist: minds.

The question of whether the mental realm exists is therefore a highly important one, not only for understanding the nature of reality, but also for understanding ourselves. This is the question that I will explore in the next few posts.

The Mental and the Physical

If I am going to answer the question of whether the mental exists in addition to the physical, I had better try to be a little more clear about those terms. In my discussion of the physical realm, I was relying on an intuitive conception of what physical means, but now that I am contrasting it with mental, I need definitions.

First I will need definitions for abstract, and I will stipulate a definition for evaluative:

  • Abstract entity: any kind of abstract object. (Such as properties, propositions, mathematical objects, etc.)
  • Abstract property: a property ascribed to an abstract object. (Such as true or false, as ascribed to propositions, or positive or negative, as ascribed to numbers.)
  • Evaluative property: a property expressing a value judgement. (Such as correct or incorrect, or good or bad.)

Then, here is my working definition of physical:

  • Physical entity: a non-abstract entity capable, in principle, of being fully characterized by a fundamental theory of physics. (Here, I think only a theory that specifies a primitive ontology is complete enough to count as a fundamental theory of physics.)
  • Physical property: a non-abstract, non-evaluative property used in the characterization of physical entities by a fundamental theory of physics, or a property that, in principle, can be described or explained fully in terms of such a theory.

And finally, my working definition of mental:

  • Mental entity: any non-abstract, non-physical entity, which may be related to mind, consciousness, thought, or any non-physical aspect of human nature.
  • Mental property: a non-abstract, non-evaluative, non-physical property, which may be related to mind, consciousness, etc.

Are these appropriate definitions? I believe my definition of physical is acceptable. The usual view of scientific realism is that physics, in the ideal limit, will describe the basic constituents that the universe is made of, and fully explain their behaviour.

Furthermore, the usual view seems to be that everything else in the universe can be analyzed in terms of its composition out of those basic constituents, and that its properties can be explained in terms of behaviour of those constituents: exactly in the way that solid materials are described by their atomic structure, and their solidity is explained by the atomic forces that prevent penetration of that structure.

With an acceptable positive definition of physical (saying what it is), my mostly negative definition of mental (saying what it is not) is in line with my purpose here: which is to explore whether something non-physical exists. Describing what it is like, though still important, is a secondary task.

The positive part of my definition of mental is intentionally vague. I am casting the net wide to start with; I will narrow it down once I have caught something. So if the broader definition I have given here includes what might be considered spiritual rather than mental, that is no matter. For now, I am not concerned with making a distinction between the two.

(Note: I can’t think of anything that might exist that does not fit somewhere into the categorization of abstract, physical, or mental/spiritual entities or their properties, or events that happen to such entities, or activities of such entities. So I think this categorization is fairly exhaustive.)

Dualism and Materialism

When I argued that the physical realm exists, the position I was arguing against was philosophical idealism: the belief that only the mental or abstract realm exists. And my argument was essentially that our experience of the physical realm provides the justification for properly basic belief in its existence, and that the existence of the physical realm is the best explanation for our experience of it.

Very similar considerations lead me to believe that the mental realm also exists, and that is what I will attempt to show in the next few posts. The position I will be arguing against now is philosophical materialism: the belief that only the physical realm exists. And again, my argument will be that our conscious experience provides justification for properly basic belief in existence of the mental realm, and that the existence of the mental realm is the best explanation for our conscious experience.

(To see my reasons for thinking that experience and inference to the best explanation are good reasons for believing something, you’ll have to go back to my exploration of truth and knowledge, where I outlined my epistemology.)

In fact, I think materialism simply fails to explain how we can have any conscious experience at all. Our conscious experience cannot be reduced to the physical realm by any means, as far as I can conceive. (Contrasting this is the explanatory power of idealism: it is still a poor explanation, but at least it makes sense to say that our experience of the physical world could all be an illusion.) So I think we can be even more confident in the existence of the mental realm than we can of the physical realm.

By rejecting both idealism and materialism, what I am embracing is a form of dualism: belief in both mind and matter. In the next few posts, I will be looking at the reasons for and against this position.

There are two main camps within dualism itself, known as property dualism and substance dualism. Property dualism holds that only physical entities exist, but that some physical entities have mental properties, distinct from and in addition to their physical properties. Substance dualism, on the other hand, holds that mental entities exist, distinct from and in addition to physical entities, and that these mental entities are what have mental properties. A subcategory of substance dualism, interactionist substance dualism, holds that cause-and-effect relations can go in both directions between physical and mental entities.

The “substance” in substance dualism does not have the meaning that we generally associate with that word. Nowadays, the word substance usually makes us think of a material-like or mass-like kind of stuff, thanks to the way the word is used in material science and chemistry. But a substance dualist does not need to believe that anything in the mental realm is composed of any kind of stuff, or that there are mental analogs of physical matter or energy.

Rather, the original meaning of substance, which is still retained in philosophical usage, is a concrete, unified entity that bears properties (it “sub-stands,” or stands under, its properties) and can endure through time and change. So that is the meaning of “substance” in substance dualism; it could perhaps be called entity dualism as an alternative.

A substance, according to this concept, is also usually thought of as being organized in a top-down kind of way, so that the identities of its parts are derived from the substance, rather than the identity of the substance being derived from its parts. In fact, a living organism is a prototypical example of a substance in this sense. But a substance dualist also does not need to think that mental substances are complex and composed of parts, the way that living organisms are: minds could just be simple entities with no separable parts (though bearing complex properties, such as conscious experiences).

I believe the evidence of our conscious experience and intuition points not only to dualism over materialism, but to substance dualism over property dualism. So, starting in my next post, I will begin to explore why I think this is the case.