The philosophical mind-body problem is relevant to religious beliefs, to Buddhist teachings and to dialectical materialism. The following discussion is an attempt to clarify some of the issues.
Brain processes cause consciousness but causality is not identity. The properties of a brain state are not those of a corresponding mental state or vice versa. For example, brain cells are grey whereas a mental image of the sun is yellow and abstract thoughts do not have colours.
A mental image or image in the mind is not a material image in the brain. A material image is an object or at least a surface that resembles another object. Examples are reflections, paintings, photographs and statues. Observation of brains does not reveal any such images inside them and, even if it did, there would be no necessary connection between such images and consciousness. Reflections etc are not conscious of the objects that they resemble. A photograph is a visual record and reminder but not a conscious memory.
Even if there were material images inside our brains, we would not be able to see them there because we do not have eyes inside our heads. Even if we were able to see material images inside our brains, that is not what happens when we imagine something. We do not visually perceive a present image but inwardly consider the visual appearance of an absent or even non-existent object. An imagined but non-existent object is "imaginary". We say of imaginary objects either that they do not exist or, alternatively, that they exist only in our heads. This phrase acknowledges the location of mental processes in the brain but does not entail that anyone who looks into a brain sees in there a host of mythological creatures or fictitious characters. If these creatures and characters existed in a way that enabled them to be seen by external observers, then they would not be mythological or fictitious and would not fit inside a head.
Even if mental images were somehow identified with material images inside the brain, most mental processes do not involve mental images. For example, we learn the meanings of words without forming a specific image for each word as we hear it, especially not for words like "if", "but", "and" etc. We understand these words if we use them correctly, not if we entertain a particular mental image each time we hear or read them. The concept of whiteness is not a white mental image but an abstraction applicable to every instance of that colour, whether real or imagined. The ability to apply concepts is described by psychologists and philosophers in terms differing completely from those used by neurologists to describe brains.
Brain states can be scientifically observed whereas thoughts can only be divulged by their thinker, who is usually unaware of his own brain processes. A scientifically studied brain is part of a person as observed by others whereas that person’s consciousness is his observations of everything else. Therefore, our description of his brain and his description of his consciousness differ.
By interacting with environments, we become conscious. By interacting with each other, we become self-conscious and detect consciousness in others. We become sufficiently conscious to recognise conscious behaviour. By studying brains, we discover not consciousness but its causes. Psychology is related, but not reducible, to neurology. Consciousness is a relationship, not an object, the process of seeing, not a seen process. (Detection, recognition, study, discovery and seeing presuppose consciousness, thus do not explain it.)
A brain can be described entirely in terms of its own physical properties, electrochemical states and immediate sensory inputs whereas consciousness cannot be described without reference to its objects which may be spatio-temporally distant, like another galaxy, a remote quasar or the cosmic origin, abstract, like a taste for autobiography, the middle of next week or the square root of minus one, unvisualisable, like a tachyon, a singularity or the fourth dimension, evaluative, like a moral judgement or an aesthetic response, or non-existent, like the Philosopher’s Stone or the Holy Grail. Merely physical acts cannot have non-existent objects: we can think about the Philosopher’s Stone but not sit on it and can look for the Grail but not drink from it.
It is impossible to describe a process, X, in such a way that the description excludes synonyms of "consciousness" like "sensation", "experience", "awareness", "perception", "knowledge", "cognition", "recognition" etc yet hearers or readers of the description remark, " ‘X’ is what we mean by ‘consciousness’ ". It follows that consciousness, like whiteness, is qualitatively unique and indefinable but not that it is inexplicable. It is explained by its material causes. Organisms became increasingly sensitive to environmental alterations until some organisms began consciously sensing their external environments, then perceiving discrete objects. Self-consciousness can be analysed into constituents which include basic concepts and conceptual abilities but also include the simple and unanalysable property of consciousness as opposed to unconsciousness. We cannot describe whiteness to a permanently blind man but need not describe consciousness to a permanently unconscious man. A person’s physical and psychological properties are two aspects of one entity, not two entities. Psychology emerges from but is not reducible to physicality.
Imagination is reified, i. e., mistakenly regarded as a purely physical process, in eight stages:
(1) We describe imagination not as a mental act but as a series of passively experienced mental images. This downplays the extent to which imagining something for ourselves differs from merely seeing an object that already exists and that is visible to others.
(2) We differentiate mental images from material objects by describing privately imagined things as "internal" and publicly perceivable objects as "external". The words "in", "inner" and "internal" are ambiguous because they differentiate the mental from the physical but also have purely physical applications. My hand is inside my pocket but both are outside my mind. The heart is an internal organ but is part of the external world from the mind’s point of view. It is not a figment of its owner’s imagination. We know this because it is detectable by others and because we find that it has continued to exist and to function even when it has not been observed.
(3) We acknowledge that mental processes are effects of brain processes.
(4) We identify the effects with their causes.
(5) We conclude that "internal" mental images are internal to the brain.
(6) Because the brain is a material organ, we conclude that an image that is internal to the brain is a material image.
(7) Because material images are visible to external observers, it is thought that a scientist observing a brain with a sufficiently sensitive instrument will be able to see in there a material image of a giraffe whenever the person whose brain he is observing imagines a giraffe.
(8) It is thought that the imagining of a giraffe is nothing more nor other than the seeing of a material image of a giraffe inside one’s own brain, although it is usually acknowledged that we cannot see anything in that direction.
This may sound implausible but I have had several heated arguments on the subject. People argue that an image must be detectable inside the brain because they think that the only alternative is to claim that the mind is independent of the brain. When this proposition is stated clearly, it is seen to be false. The mind may depend on the brain whether or not there are material images in the brain. All that the scientist needs to observe in the brain is whatever neurological process causes a mental act of the imagination. There need not be a visible resemblance between the physical cause and its psychological effect.
The brain is not divided into one part that is the observing subject and another part that is observed objects. Instead, the whole brain is somehow involved in generating consciousness, first of the external world, then of an internal realm that is not merely visual and that cannot be read in the brain in the way that words are read in a book. Conceivably, a scientist might record a person’s entire brain state at a particular moment, receive from the person, perhaps by hypnosis, an exhaustive account of his mental state at that moment and correlate the two states. However, every moment of consciousness is unique. Further, brains function differently and dynamically.
Therefore, even a large number of specific brain-mind correlations would not necessarily enable a scientist observing a future brain state to describe the corresponding mental state. Further, even if he were able to do this, he would still be inferring a mental state from an observed brain state, not directly observing the mental state.
As a single water molecule is not wet, so a single brain cell is not conscious. As Hegel argued, quantity affects quality. Cerebral processing of environmental inputs became complicated (a quantitative change), then conscious (a qualitative change). Unconscious organisms and their environments became conscious subjects and their objects.
If natural brains cause consciousness, then so would artificial brains. However, rule-governed manipulation of symbols is not knowledge of their meanings and simulation is not duplication. Therefore, analogue computers are not artificial brains.
The qualitative difference between psyches and brains entails at least the logical possibility of a bodiless psyche. Just as there are unconscious material objects, there could be immaterial conscious subjects. We can, without self-contradiction, imagine a person losing all his physical properties of size, weight, mass etc while retaining his mental abilities to perceive, remember, think etc. We would then say either that his body had become invisible and, more generally, undetectable or that he had become bodiless. He would see without eyes or a brain. There is only an empirically contingent, not a logically necessary, connection between possession of bodily organs and the familiar experience of direct acquaintance with the visual properties of material objects. We can, as an imaginative exercise or thought experiment, conceive of experience without organs whereas we cannot, for example, conceive of a triangle without three sides. Fictitious accounts of disembodied subjects and real life accounts of alleged "out of the body" experiences are regarded as contrary to common experience but are not usually dismissed as verbally incoherent as a phrase like "square triangle" would be with the result that no one thinks of using such a phrase whereas people can and do imagine leaving their bodies.
If the relationship between brain states and consciousness is causal, then it is an empirically discerned constant conjunction between brain states and consciousness, not a necessary implication of the meanings of the words used to describe either brains or consciousness. Any empirically known generalisation is contingent, i.e., could have been otherwise. When a generalisation is necessary, i. e., could not have been otherwise, then we recognise its necessity simply by considering the meaning of the general statement, e.g., "all white men are men", and do not have to settle the matter experientially, i.e., by observing all white men in order to check whether one of them turns out not to be a man. The general statement that brains cause consciousness is known empirically. Of course, if, knowing that brains in fact cause consciousness, we then define a brain as that which causes consciousness, then the proposition that brains cause consciousness becomes a tautology or logical necessity but matters of fact about the world are not settled merely by defining words. If a brain is defined as the organ inside the skull, then it remains possible, first, that some brains will be found to control only automatic and unconscious responses of organisms to their environments and, secondly, that some instances of consciousness could have causes other than brains.
Violation of causal laws is physically impossible, i.e., we confidently predict that a violation will not occur because it would contradict all past experience and scientific knowledge. However, a violation is logically possible, i.e., we can conceive of its occurrence. Otherwise, stories about magic and miracles would be not false or fictitious but incomprehensible. Even in the real world, it is conceivable, first, that causal laws could vary in different cosmic epochs and, secondly, that there can be occasional exceptions, e.g., irregularities resulting from random "quantum" fluctuations. The possibility of consciousness independent of brains cannot be ruled out a priori.
However, disembodied consciousness remains merely a logical possibility. The experienced actual world is only one of many logically possible worlds. Other such worlds would contain different physical properties, natural laws or historical events or even different relationships between consciousness and its objects, e.g., a world composed entirely of approaching and receding sounds and of a hearer who, if he hears a particular sound continuously and identifies himself with it, thereby regards it as his body but who, otherwise, would have no reason to think that consciousness could be embodied.
In the world that we do inhabit, however, most empirical evidence supports the proposition that consciousness not only is caused by but also remains dependent on physical processes in visible and tangible brains. "Out of the body" experiences are possibly altered states of consciousness in which bodily sensations are disregarded and the immediate environment is vividly imagined as if seen from a point outside the body. "Near death" experiences are "out of the body" experiences that occur while the clinically dead body remains intact and revivable. Therefore, they do not guarantee continued consciousness after the body’s irrevocable decay. If a medium says what only X, who is dead, could have known, this could mean that X is disembodied and speaking through the medium but could also mean that we were wrong to think that only X could have known it. However, I have not studied the body of prima facie evidence for communications from the dead and therefore cannot comment further.
Only embodied subjects can be objects of each other’s consciousness. Only subjects that are also objects can participate in communities. Only participation in a linquistic community teaches individuals how to use words and other symbols consistently, therefore meaningfully. Only words and symbols enable individuals to think about things that are not immediately present. Only thought about objects of consciousness that are past, future, absent, hypothetical, imagined, general etc differentiates abstract thought and reflective self-consciousness from immediate animal sensation. Therefore:
any disembodied subjects that are capable of abstract thought and reflective self-consciousness must originally have been embodied;
any disembodied subjects that enter a common environment where they can communicate with each other are somehow re-embodied;
the dialectical materialist principle that consciousness is based in a form of being, i.e., in an objective realm independent of consciousness, applies even to a hypothetical hereafter.