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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 has two principle 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.
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. 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 and the "homunculus argument"Edit
Children tend to believe that the world is identical to the world that they see and feel. A very young child might even think that a curiously shaped shadow is a monster or be fooled into thinking that there really are people inside a television set. Older children with a smattering of geometry tend to believe that they have a 'point eye' that sees the world. Physical considerations show that ideas such as these are 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 exist at a single point. Some of the discrepancies between the physical reality and our experience are shown in the illustration below. File:Constudnaive.gif
The illustration shows 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?
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.
The "homunculus argument" is also discussed in depth in the text. Readers may have come across this argument and be convinced that they have understood it. The popular version of this argument proposes that if what we experience is something like an image in the brain then there would need to be a little person, or homunculus, in the brain to view the image and then there would need to be a little person within this homunculus to view the image in the head of the first homunculus and so on indefinitely. This popular version suggests that data is transferred from the world to the brain and then must be transferred again into an homunculus to be viewed. However, contrary to the popular interpretation the homunculus argument does not demonstrate that there are no images in the brain. Given that homunculi do not exist it actually demonstrates an intuition that conscious experience is not due solely to data transfer. Interpreting the homunculus argument as a proof that conscious experience could not be in the brain is equivalent to rejecting the possibility that there may be some physical phenomena involved in conscious experience other than material transfers and should be treated with caution.
This material has been imported fom the wikibook "Consciousness"under the GNU Free Documentation License.