Everyone has their own view of the nature of consciousness based on their education and background. The intention of this book is to expand this view by providing an insight into the various ideas and beliefs on the subject as well as a review of current work in neuroscience. The neuroscientist should find the philosophical discussion interesting because this provides first-person insights into the nature of consciousness and also provides some subtle arguments about why consciousness is not a simple problem. The student of philosophy will find a useful introduction to the subject and information about neuroscience and physics that is difficult to acquire elsewhere.
It is often said that consciousness cannot be defined. This is not true; philosophers have indeed defined it in its own terms. It can be described in terms of two principal components: firstly phenomenal consciousness which consists of our experience with things laid out in space and time, sensations, emotions, thoughts, etc., and secondly access consciousness which is the processes that act on the things in experience. Phenomenal consciousness is much like the “perceptual space” of psychological and physiological research. It is the many simultaneous events that become the space of experience in general and it is now a legitimate target of scientific research.
As will be seen in the following pages, the issue for the scientist and philosopher is to determine the location and form of the things in phenomenal consciousness and even to consider whether such a thing could exist. Is phenomenal consciousness directly things in the world beyond the body, is it brain activity based on things in the world and internal processes — a sort of virtual reality — or is it some spiritual or other phenomenon?
A note on Naive Realism 
The study of consciousness may seem to be esoteric or outside of the main stream but it includes some very real problems in science and philosophy. The most obvious problem is how we can see anything at all. Many people with a smattering of geometry tend to believe that they have a 'point eye' that sees the world and this idea is known as perceptual "Naive Realism". Physical considerations show that this idea is highly contentious; we have two eyes with different images in each, normally the only images in the world are created by optical instruments such as the eye and the photons that carry light to the observer cannot and do not all converge at a single point. Some of the discrepancies between the physical reality and our experience are shown in the illustrations.
The naive realist idea of perception involves a point eye looking at a geometrical form. But the physics is different; there are two eyes with sometimes very different images in each. Light is refracted over the entire area of the cornea and directed over the entire area of the retina - there is no 'point eye'.
The cloud of photons that compose light must get in the way of the view but naive realism neglects this, regarding the photons as somehow transparent yet gathering as an impossible group of millions of photons in a viewing point.
Light rays go everywhere, it is only after light has passed through an optical instrument such as the eye that an image is formed. Hold up a sheet of paper - there are no images on it.
The illustrations show the nature of one of the most difficult problems studied by neuroscience: how can the images on the two retinas become experience? How can we imagine things or experience dreams and hallucinations? Studies on the neural basis of binocular rivalry and MRI studies of imagination are leading the way in our comprehension of these problems but there is still no physical theory that is congruent with sensory experience. The problem of binding also takes us further from Naive Realism; we experience speech at the mouth of the speaker even though we might be listening through headphones, how is sound, touch etc. bound to vision? The objective of the scientific study of consciousness is to discover how we convert data from the world into our experience.
A degree of Naive Realism is a sensible idea for coping with the everyday problems of working and living. Most physical scientists and people in general are, to some extent, Naive Realists until they study the biology of sensation and the problems of perception and consciousness. There is often a suspicion, or even fear, amongst Naive Realists that any analysis of conscious experience is a suggestion that the world does not exist or everything is imaginary. These fears are unfounded: Neuroscience is a study of the part of the physical world represented by brain activity and is part of medicine.
Intended audience and how to read this book 
This book is intended as a complementary text for neuroscience and philosophy degree courses. The book is divided into four parts. If you are not interested in some part, skip to the next. The first part is a detailed historical review of the philosophy of phenomenal consciousness. The second part is a discussion of philosophical theories, it is intended to be challenging and even irritating. Philosophy undergraduates are encouraged to criticise and react to this part. The third part is a review of the neuroscience of consciousness and is suitable for undergraduate studies in the field. The end of the book is a discussion of theories of consciousness.
Being freely available to all students the book can serve as a source for seminars even if you disagree with the content i.e.: “Why is (a given section) an oversimplification/biased/out of date etc.?”
The text covers a difficult area that straddles the humanities and science faculties. It is probably more oriented towards the scientist who needs a scientific insight into philosophical theory rather than vice versa. It is suitable as a supplementary text for the following undergraduate modules, units and courses:
- Neurophysiology/Neurobiology modules (physiology of perception, physiology of consciousness, neuronal basis of consciousness)
- Neuropsychology modules
- Neuroanatomy modules
- Cognitive psychology/Cognitive science
- Psychology of consciousness
- Psychology - behaviourism vs cognitivism debate
- Philosophy of mind and metaphysics
- Computing - Artificial intelligence and consciousness
- Consciousness studies courses
This is a “Wikibook” and, in this edition, has more breadth than depth. In some areas, particularly in the huge field of the philosophy of consciousness, topics are introduced and the obvious flaws or successes pointed out but a fully referenced, in-depth treatment is sometimes absent at this stage. We need your help and contributions from scholars in the field are invited. Please contribute but please, at the very least, scan the book first to ensure that your prospective contribution has not been included already! In particular contributors who wish to write “all self respecting scientists think that the brain is a digital computer” should read the section on information theory and add their contribution to the section on the possibility of conscious digital computers.