Consciousness

The Science of Subjectivity

Antti Revonsuo

• Publisher: Psychology Press
• Year: 2009
• ISBN:
  9781135164799
• Edition: 1
• Topic: Psychology
• Subtopic: History & Theory in Psychology
• Index: Psychology

The study of consciousness is recognized as one of the biggest remaining challenges to the scientific community. This book provides a fascinating introduction to the new science that promises to illuminate our understanding of the subject.

Consciousness covers all the main approaches to the modern scientific study of consciousness, and also gives the necessary historical, philosophical and conceptual background to the field. Current scientific evidence and theory from the fields of neuropsychology, cognitive neuroscience, brain imaging and the study of altered states of consciousness such as dreaming, hypnosis, meditation and out-of-body experiences is presented. Revonsuo provides an integrative review of the major existing philosophical and empirical theories of consciousness and identifies the most promising areas for future developments in the field.

This textbook offers a readable and timely introduction to the science of consciousness for anyone interested in this compelling area, especially undergraduates studying psychology, philosophy, cognition, neuroscience and related fields.

Part one
Background to the science of consciousness

Chapter 1
The philosophical foundations of consciousness science

Introduction 4

1.1 The first distinction: Dualism and monism 4

1.2 Dualistic theories of consciousness 5

1.3 Monistic theories of consciousness 16

1.4 Why the mind–body problem will not go away 39

Chapter summary 44

Further reading 45

Brief discussion questions 45

Introduction

In philosophy, the mind–body problem, or the relationship between the inner mental world and the external physical world, has been discussed for thousands of years. What is the human soul, or the mind, or consciousness? What is its relationship to the body, the brain or physical matter in general? In some theories, the nature of consciousness (subjective psychological reality) and the nature of the brain (objective physical, biological reality) are seen as fundamentally different: made out of very different kinds of basic stuff. That solution makes it all the more difficult to explain how the two could be in close causal interaction with each other. Alternatively, other theories assume that consciousness and the rest of reality are not tremendously different after all, but consist of the same basic stuff. The problem for the latter is to show how consciousness could be just the same as ordinary physical matter – or vice versa! In addition to the mind–body problem, the science of consciousness also has to face the other-minds problem: How can we know about other minds? We cannot directly perceive, detect or measure the presence of consciousness. We do not seem to have any scientific access to the subjective psychological realities of other creatures. Thus, are they beyond science altogether?

1.1 The first distinction: Dualism and monism

We will first divide the philosophical mind–body theories into two different categories, dualistic theories and monistic theories.

Definition of dualism

All dualistic theories say that the world (the universe as a whole) consists of two categorically different types of entity or substance. One of them is physical. This substance constitutes physical matter, energy, force fields, elementary particles and forces, and all the rest of the things that the physical sciences take as the fundamental building blocks of the universe. In the final analysis, the more complex physical systems, such as stars, mountains and trees, consist of the elementary physical entities.

The other substance is mental by nature. “Mental” is taken by definition to be something nonphysical, something entirely different from the physical rather than a part or a variety of the physical. It is less clear what the mental substance is supposed to consist of, but it seems natural to assume that, whatever it is, it must be the same sort of stuff that forms our subjective psychological reality. Thus, the mental stuff consists of subjective, qualitative states of consciousness located within the mental space where conscious events happen. It is directly present for us in our sensations, percepts, thoughts, emotions, images, as they are subjectively experienced in the stream of consciousness. Typically, the nonphysical substance is depicted as some kind of ghostly mind-stuff or soul-stuff that is independent of physical matter and even of the laws of nature that govern the physical realm. Soul-stuff is presumed to be beyond all objective physical measurements and observations, consisting perhaps of extremely fine, ethereal “soul-atoms” that are unlike any physical particles, or existing in a mental “soul-space”, another dimension altogether that lies beyond the physical space–time.

Definition of monism

By contrast, all monistic theories say that the world (the universe as a whole) consists of only one type of substance. Different monistic theories, however, disagree about the ultimate nature of the fundamental substance. Some say that the universe is at bottom thoroughly physical (materialism or physicalism), whereas others say that the universe consists of nothing but mental substance across the board (idealism). Yet others claim that the universe is, at the rock bottom level, neither “mental” nor “physical” (neutral monism). We will return to these distinctions in due time. Now we will first explore dualistic theories of consciousness in more detail.

1.2 Dualistic theories of consciousness

Dualistic theories take it for granted that both physical matter and subjective consciousness are real phenomena that exist in their own right. Neither owes its existence to the other; they are both on an equal footing in the universe. They are just radically different kinds of stuff. This is one of the inviting characteristics of dualistic theories. They show due respect both to the external physical world – basically accepting all the physical sciences, as far as they go – and to our inner subjective world, saying that it is a reality of its own, beyond the physical one.

But dualistic theories also have some serious weaknesses. First, they have difficulty in telling us exactly what kind of stuff the nonphysical soul-stuff is supposed to be and where it is located in relation to physical space. They only tell us what it is not: it is not physical – it is nonphysical. But what is it to be nonphysical or immaterial? If our consciousness is based on nonphysical soul-stuff, then we need a testable scientific theory that describes and explains exactly what soul-stuff is, how it behaves and where it is to be found. Therefore, dualistic theories are not necessarily able to offer us terribly convincing answers to the ontological problem, enquiring about the basic nature of consciousness. What is worse, they are also in trouble when trying to answer the relational question: How exactly does the nonphysical soul-stuff relate to the physical world, especially to our bodies and brains?

If we know anything about the relationship between consciousness and physical reality, it is that those two realms seem to collaborate seamlessly whenever we perceive external objects or whenever we perform voluntary actions. On the one hand, the sensory organs in our bodies receive physical energy from the world and convert it to neural signals that in some way are transformed to subjective sensations and percepts in our inner psychological world. On the other hand, we formulate thoughts and plans and we experience desires and cravings in our consciousness. By a mere act of will we can make our physical muscles, limbs and bodies move through physical space, guided by our conscious will and intention. There seems to be a two-way interaction between consciousness and physical reality: first, the external world reaches into our consciousness, which thereby senses and perceives the world; second, our mind reaches out to the external world and thereby guides the behaviour of the body at will.

Usually dualistic theories are differentiated from each other on the basis of how they answer the relational question, or how exactly does the nonphysical soul-stuff relate to the physical world, especially to our bodies and brains? The three main alternatives are known as interactionism, epiphenomenalism and parallelism.

Interactionism

The main idea in interactionism is, as the name hints, that there is two-way causal interaction between the external physical reality and the subjective psychological reality, or brain and consciousness. In other words, physical stimuli in the external world (e.g. electromagnetic energy such as light) first hit sensory organs (such as the retina in the back of the eye), then the signal is transformed into neural impulses that travel to the brain, especially the visual cortex in the backside of the brain, and there at some stage, veiled in mystery, the physical brain activation gets in touch with the nonphysical soul-stuff or consciousness, thus causing us to have the subjective experience of seeing. This is the “bottom-up” causal pathway leading from physical input into conscious output. The “top-down” causal pathway (also called “mental causation”) travels in the opposite direction, leading from conscious input (a thought, a desire or an intention to act) to physical output. To take an example, let us say you feel a sudden strong urge to eat chocolate. The desire is a conscious experience. It causes you to look around for the chocolate bar and then, when you spot it, causes your hand to reach towards the bar, grab it quickly, move it into your mouth and sink your teeth into it. A conscious experience thus caused physical changes, first in the brain and then in the neural messages travelling from the brain to the muscles and finally these changes created physical movements of your body.

Often in our everyday behaviour the bottom-up and top-down causal pathways form interactive sensorimotor loops. If you step on a thorn barefoot, the signals from your foot travel quickly to your brain and you experience the pain in your foot and a strong urge to stop the pain. Then you try to locate the source of the pain, you look and touch the sore spot and when you spot the thorn sticking painfully there you pull it out in relief. If you walk on a strawberry field, looking for ripe red strawberries, when you see one (as a result of neural activity in the bottom-up pathway from the retina to the visual cortex to consciousness) you reach out to pick it (as a result of activity in the top-down pathway, from conscious perception and desire to overt physical behaviour).

The causal interaction between the physical and the nonphysical realms seems to work rather smoothly. In fact, in our everyday behaviour we never even need to think about it. We just open our eyes and let the physical stimuli flow in, resulting in conscious visual experience. We use our physical bodies to carry out our intentions and desires and all this seems to work absolutely flawlessly. The problem is to explain how exactly two radically different realms – physical processes such as neural activity, and nonphysical qualitative vibrations of the soul such as our sensations, thoughts and desires – could interact at all, let alone so smoothly. That is, the interactionist approach owes us a scientific theory, at least a preliminary one, concerning the actual mechanisms that mediate between the two worlds.

Well, why does not the interactionist then provide us with a theory or a description of the mechanisms? The trouble is that the physical realm is causally closed and, respectively, the nonphysical realm is causally inert (at least with respect to the physical). The causal closure of the physical world means that physical events can only be causally influenced by other physical events, and are able to cause further events only of the purely physical kind, through mechanisms that are themselves nothing but physical. Causation requires mechanisms that have physical properties, such as mass, energy, force fields, physical motion through physical space, and so on. The causal inertia of consciousness means that our experiences, if they are thoroughly nonphysical, have to be unnecessary for any physical events to happen and in fact they must be inherently incapable of moving or influencing anything in the physical world whatsoever, including neural activities in our brain. If consciousness consists of ghostly soul-stuff, then, like the prototypical ghosts, it will simply slide through all material things without having any effects on them!

The problem that the dualist faces is this. To causally interact with the physical realm (such as the brain), a thing needs to have at least some physical properties. Thus, soul-stuff should have some physical properties after all if it is to have any impact on our brain activity. But for the dualist consciousness is by definition something nonphysical. How could something thoroughly nonphysical, something devoid of mass, energy, motion, gravity, spatial extension and location and all imaginable physical features, cause anything at all to happen in any objects of the physical world, such as the brain? How exactly does soul-stuff pull the physical strings in the brain to actualize a physical manifestation of its free will? This is a complete mystery. Unless a convincing scientific hypothesis of the mechanisms working between the soul and the brain can be put forward, interactionism remains pure metaphysical speculation that can only be afforded within philosophy, not playing any part in the empirical science of consciousness.

The problem of explaining the nature of the two-way interaction between consciousness and brain is not the only problem for interactionism, although it is perhaps the most difficult one. Other problems arise when we attempt to fit the dualist view of consciousness in the scientific world-view with all the other branches of empirical science, such as evolutionary history (phylogeny), individual development (ontogeny) and neuropsychology. At what point in evolution did the immaterial soul-stuff for the first time become causally attached to biological organisms? How and why did that happen if divine intervention is not allowed? When did the first living creature get a soul, turning into a conscious being that could “see the light” and feel its own existence? Presumably, before that grand moment in the history of life on Earth, every creature on this planet had been a totally nonconscious zombie, a mere biological mechanism without any inner mental life. A similar question can be asked with regard to a human fetus or baby: When, how and why does the soul-stuff make a connection to its developing brain? When does the baby “see the light” of subjective existence for the very first time?

Soul-stuff alone is supposed to be able to turn mere biomechanical zombies into conscious human beings with an inner subjective life. Thus, there is a pressing need to find the answers to the questions concerning the emergence of the inner life in evolution and child development. At the same time it is very difficult to pinpoint any stage either in evolutionary his...