In this post I will explain why I think that certain forms of realism about conscious experience face some issues that ultimately lead them to the conclusion that our belief that consciousness exists is not reliable, and thus consciousness may not exist at all, as counterintuitively as it seems. This conclusion is similar to the one given by the illusionist theory of consciousness, a kind of eliminativism about qualia, which entails that conscious experience does not exist.
First of all, we need to briefly define what these two views consists in. This is the definition of epiphenomenalism found of Wikipedia :
Epiphenomenalism is a position on the mind–body problem which holds that subjective mental events are completely dependent for their existence on corresponding physical and biochemical events within the human body, yet themselves have no influence over physical events. The appearance that subjective mental states (such as intentions) influence physical events is merely an illusion, consciousness being a by-product of physical states of the world. For instance, fear seems to make the heart beat faster, but according to epiphenomenalism the biochemical secretions of the brain and nervous system (such as adrenaline)—not the experience of fear—is what raises the heartbeat.[1] Because mental events are a kind of overflow that cannot cause anything physical, yet have non-physical properties, epiphenomenalism is viewed as a form of property dualism.
Indeed, epiphenomenalism supposes a property dualism which holds that although the world is constituted of one kind of substance that is the physical kind, or matter, there exists two kinds of properties : first, physical properties (mass, electric charge etc.), which are described by physics. They can be measured and are publicly observable. Second, there are mental properties, which constitute our subjective conscious experience. These are essentially private and not publicly observable ; no measuring device or no one else than myself could ever access my conscious experience itself, apart from its behavioral or neurological correlates, which are physical states.
Eliminative materialism, or simply eliminativism, is the view that most mental states as we refer to them in our common everyday langage, such as beliefs and desires, (these states are called propositional attitudes) are poorly defined and must be eliminated, since they don't match any coherent neural basis, the same way chemists eliminated the concept of phlogiston since it does not match any chemical reality. This is eliminativism about propositional attitudes, a rather weak version of eliminativism.
Some stronger versions of eliminativism entails that we must eliminate not only many psychological concepts but also qualia, the instances of subjective conscious experience, for instance pain as "what it is like" to burn one's hand or taste as "what it is like" to eat chocolate. This is eliminativism about qualia.
Illusionism assumes eliminativism about qualia, and explains how our strong belief that qualia does exist is mislead. We are victims of an illusion by thinking of consciousness exists, as a subjective experience distinct from neurobiological processes, whereas it does not. One of the main arguments to support this view is the debunking argument against consciousness : we can explain our intuition that consciousness exists without assuming that it actually does, simply referring to neurological introspective processes that induces the belief that we are conscious beings. Whether phenomenal consciousness actually existed or not, we would still have this belief ! Therefore, there is no reason to postulate that it exists and thus entail a number of problems related to the existence to this non-physical property or substance : for instance, its radically different nature from physical matter, its relation with the brain and so on.
Let's talk about the indubitability of consciousness. According to this fairly widely-endorsed principle, conscious states, when experienced by a subject, cannot be doubted of their existence. When I feel pain, I should be certain that the pain I feel exists. If it seems like i’m feeling pain, it is not possible that this pain as a subjective counscious state does not actually exist. I can be wrong about what this conscious experience means about the painful area : I might be wrong about what this pain means : I may feel like my leg is broken whereas it is only bruised, or even in the hypothetical case where my brain is sent similar signals as the ones it would revcieve if my leg was injured, as it can happen in the phantom limb condition for instance. However, I cannot doubt that I experience the particular feeling of pain I am having at the moment. If it merely feels to me like I have a certain conscious experience, then there actually is a conscious experience.
In what follows, I will argue that in order to be justified to assume that my conscious experiences exists, these conscious states need to produce markers of their existence in physical matter, more specifically inside the brain. This is a necessary condition without which we cannot assess their existence.
Given this condition, my point is : since epiphenomenalism rejects the possibility for conscious states or qualia to cause effects on matter, it follows that we are not justified to think that our mental states exist. Thus, epiphenomenalism rejects the indubitability principle. Let’s detail how in what follows.
In science, when trying to reveal the existence of a phenomena, event, or object, we try in many cases to find « markers » of these entities on their environment. We try to measure these markers with measuring devices, or eventually observe them directly. In order to do that, we conduct experiments in which specific markers will eventually be found.
According to the theory in which a given entity fits in, we can predict what behaviour it will have : under known conditions, it will cause other predictable physical events, which the experimenter will seek to observe or measure.
Note : this works in a more or less mediate way : eventually, the phenomenon will have effects that will themselves cause other effects, and these last effects will be observable or measurable. By the way, measuring itself works with this marker principle : the height of a thermometer is a marker of the dilation of the quicksilver inside it, that is itself a marker of a given temperature.).
Consider a cloud chamber, a particle detector used to detect inonizing radiation, that consists of a sealed environment containing supersaturated vapor of alcohol or water.
We can reveal radiation from of a material using such a cloud chamber, by observing condensation trails in the chamber caused by the radiated particle. These condensation trails highlight radiation from the material, which we cannot directly observe. These effects on vapor that are caused by radiation are evidence of radiation, which is stricto sensu impossible to observe itself. The same goes with atoms, electrons, magnetic fields…This principle actually applies generally : in numerous cases and especially when dealing with entities we can’t observe with the naked eye (too small, too distant, or somehow unable to trigger our human senses). We often cannot directly observe a physical phenomenon or object, we infer its presence from the causal effects attesting to its presence.
Note that this is not only involved in scientific study but also in everyday life. This is how vision works, for instance, as for the other senses. When viewing an object, photons from ambient lighting interact with the object in front of us and then strike our retina. There is a causal physical interaction occuring between the object and the photons, and then between the photons after they interacted and the retina. Colors and shapes of objects are interpreted from photons coming from it, after being altered by the way the object causally interacted with these photons.
This is even more clear when studying the universe : our only way to get information about celestial objects is by capturing the electromagnetic radiation they emit with telescopes. Since it is impossible to simply "see" the whole spectrum of electromagnetic radiation emitted by celestial bodies since it is mostly out of the visible range, we usually have to try to detect their radiation in the form of radio waves, which our devices can detect. The characteristics of these radiations act as markers, to assess the physical characteristics of the objects we are dealing with, such as chemical composition : this can be deduced thanks to some theory regarding how chemical composition affects electromagnetic spectrum.
Since the speed of electromagnetic radiation is finite and nothing can travel faster, we are so to speak causally isolated from celestial bodies whose light has not had enough time to reach us. Therefore, we have no way of knowing whereas they even exist or not, without being able to observe any manifestation of their existence through our measuring devices nor our senses.
Let us return to the main problem. Let’s take for granted that phenomenal consciousness exists (supported by the indubitability thesis) and works as an epiphenomenon : conscious states are caused by physical brain states, and does not have causal effects on matter in return. According to epiphenomenalism, my belief that consciousness exists, as a conscious state, is an epiphenomenon associated with and caused by the physical correlate of the belief, i.e. brain functions whose role are to form and hold beliefs. It is by virtue of the physical implementation of this belief in this specific part of my brain that it can be mobilized ; that is, influence other beliefs, interpret new information or sensory data, be reported verbally...
In respect with the « marker principle », one’s belief that their conscious states exists, in order to be accurate, need to be based on markers of these conscious states. In other terms, the fact that there is a conscious experiences must leave a physical trace that would testify to their existence in order for someone or something to assess its existence. There must be some way of telling the difference between the situation in which there actually is consciousness from the situation in which there is not. If it were accurate, a belief formation mechanism would act as a measuring device tracking markers from the presence of these conscious states.
However, epiphenomenalism admits that conscious states have no causal power. If so, they can’t leave a trace of their existence in a brain region responsible for detecting the physical signatures of conscious states, in order to create the belief in their existence. In other terms, given the epiphenomenal characteristics of consciousness, there can’t be a device, namely a brain function, that would detect markers of consciousness since these can’t make any difference to the physical world whether they actually existed instead of not.
Consequently, the formation of the belief - that we all have - according to which there exists conscious states cannot accurately guarantee the presence of conscious states because it would need the capacity for these to produce markers, which they can’t since they does not have any causal effects.
In conclusion, if epiphenomenalism is true, our belief in the existence of conscious states is not reliable. It might seem highly counterintuitive to all of us, for sure, but such a strong intuition that we all have, that is that we are at the moment the specators of an « inner movie » inside our heads made out of emotions, sensations, ideas… May be wrong if we assume the epiphenomenal nature of conscious states.
If we go a step further, this leads us to the conclusions drawn by the illusionist view on consciousness : our beliefs that consciousness are not accurate, given that these beliefs are produced through introspection which is not a reliable faculty to know whether there actually is consciousness or not. Given the conceptual challenges that arise when assuming the existence of consciousness as a non-physical property (or substance according to some versions of dualism), it may be more reasonable to assume that phenomenal consciousness does not in fact exist at all : only our belief that such a thing exists actually exists.