1. Introduction

Consciousness is extremely important to us. Without consciousness, there is just nothingness, death, night. It is a crime to kill a person who is potentially conscious. Permanently unconscious people are left to die. Religious people face death with hope because they believe that their conscious souls will break free from their physical bodies.

We know next to nothing about consciousness and its relationship to the physical world. The science of consciousness is mired in philosophical problems. We can only guess about the consciousness of coma patients, infants and animals. We have no idea about the consciousness of artificial systems.

This book neutralizes the philosophical problems with consciousness and clears the way for scientific research. It explains how we can develop mathematical theories that can make believable predictions about consciousness.

The first obstacles that need to be overcome are the metaphysical theories of consciousness. Some people claim that consciousness is a separate substance; other people believe that it is identical to the physical world. These theories generate endless debates and it is very difficult to prove or refute them. This book eliminates some of these theories and suspends judgement about the rest.

The next obstacle is the hard problem of consciousness. This typically appears when people try and fail to imagine how colourful conscious sensations are related to the colourless world of modern physics. This book breaks the hard problem of consciousness down into a pseudo problem, a difficult problem and a set of brute regularities.

Some problems with consciousness cannot be solved. For example, we cannot prove that a person is conscious. These problems affect our ability to measure consciousness through first-person reports. This book neutralizes these problems by making assumptions. The results from the science of consciousness can then be considered to be true given these assumptions.

When these obstacles have been overcome the scientific study of consciousness becomes straightforward. We can measure consciousness, measure the physical world and look for mathematical relationships between these measurements. We can use artificial intelligence to discover mathematical theories of consciousness.

Eventually we will discover mathematical theories that map between states of consciousness and states of the physical world. We will use these theories to make believable predictions about the consciousness of infants, animals and robots. We will measure the consciousness of brain-damaged patients. We will build conscious machines, repair damaged consciousnesses and create designer states of consciousness.

The scientific study of consciousness is clarified by this book. As you read it the philosophical problems will dissolve and you will gain a clear vision of consciousness research. You will no longer worry about whether consciousness is a separate substance. You will not be troubled by a desire to reduce consciousness to particles or forces. You will understand that a scientific theory of consciousness is a mathematical relationship between a formal description of consciousness and a formal description of the physical world.

This book starts with a definition of consciousness. In daily life we treat colour, sound and smell as objective properties of the world. Over the last three hundred years science has developed a series of interpretations of the world that have stripped objects of their sensory properties. Apples used to be red and tasty; now physical apples are colourless collections of jigging atoms, probability distributions of wave-particles. The physical world has become invisible. When science eliminated sensory properties from the physical world it was necessary to find a way of grouping, describing and explaining the colours, sounds and smells that we continued to encounter in daily life. We solved this problem by inventing the modern concept of consciousness. ‘Consciousness’ is a name for the sensory properties that were removed from the physical world by modern science.

The next chapter examines some ‘hard’ problems with consciousness. First, it is impossible to imagine the relationship between consciousness and the invisible physical world. Second, we find it difficult to imagine the connection between conscious experiences of brain activity and other conscious experiences. Third, there are brute regularities between consciousness and the physical world that cannot be broken down or further explained. None of these problems are unique to consciousness research. They can also be found in physics and they do not affect our ability to study consciousness scientifically. We can measure consciousness, measure the physical world and look for mathematical relationships between these measurements.

Scientists measure consciousness through first-person reports, which raises problems about the reliability of these reports, the possibility of non-reportable consciousness and the causal closure of the physical world. The fourth chapter addresses these issues by making assumptions that explain how consciousness can be measured. First, we need to identify the systems that we believe are conscious. Then we need to make other assumptions to ensure that consciousness can be accurately measured in these systems.

The fifth chapter explains how we can develop mathematical theories of the relationship between consciousness and the physical world. Scientists have carried out pilot studies that have looked for correlations between consciousness and brain activity. We are now starting to create compact mathematical theories that can map between physical and conscious states. Computers could be used to discover these theories automatically.

Chapter 6 discusses theories that link consciousness to patterns in physical materials—for example, electromagnetic waves or neuron firing patterns. With physical theories the materials in which the patterns occur are critical—if the same patterns occur in different materials, they are not claimed to be linked to consciousness. Physical theories of consciousness are similar to scientific theories in physics, chemistry and biology.

Some people have claimed that information patterns are linked to consciousness, regardless of whether they occur in a brain, a computer or a pile of sand. The seventh chapter shows that this approach fails because information is not a property of the physical world and any given information pattern can be extracted from both the conscious and unconscious brain. Information theories of consciousness should be reinterpreted as physical theories of consciousness.

Other people believe that consciousness is linked to the execution of computations. They claim that some computations are linked to consciousness regardless of whether they are executing in a brain or a digital computer. Chapter 8 argues that computations cannot be linked to consciousness because computing is a subjective use that we make of the world. Computation theories of consciousness should be reinterpreted as physical theories of consciousness.

Chapter 9 explains how theories of consciousness can be experimentally tested. This can only be done on systems that we assume are conscious, such as normally functioning adult human brains. We can also use our theories of consciousness to make deductions about the consciousness of brain-damaged people, animals and robots. These deductions cannot be verified because we cannot measure the consciousness of these systems.

When we have discovered a reliable theory of consciousness we will be able to use it to modify and enhance our consciousness. For example, we could change the shape of our conscious body or increase our level of consciousness. Chapter 10 explains how we can use a theory of consciousness to identify the physical state that is linked to a desired conscious state. If we could realize this physical state in our brains, we would experience the desired conscious state. It will be many years before this will become technologically possible.

The eleventh chapter suggests how a reliable theory of consciousness could be used to create conscious machines and make believable deductions about the consciousness of artificial systems. Silicon brain implants and consciousness uploading are interpreted as forms of machine consciousness, and the chapter discusses whether conscious machines could threaten human existence and how they should be ethically treated.

The conclusion summarises the book, highlights its limitations and suggests future directions of research. The appendix lists the definitions, assumptions, lemmas and constraints.

The main text of this book is short and self-contained and can be read through without referring to the endnotes or bibliography. The endnotes contain more detailed discussions of individual points and full references to the scientific and philosophical literature.