There is only one way of being undiseased: not having any diseases. If there were only one disease, there would be only one state of being ill: it would be having that disease. In reality, there are many diseases and therefore many ways of being ill. Is the pair consciousness/unconsciousness more like diseased/undiseased in a world with one disease or many? In other words, are their ways of being conscious in the same way as there are ways of being unconscious? It seems there are. So what are the states of consciousness?
All the states of unconsciousness are privative derivatives of consciousness i.e. they lack consciousness entirely.
Q: Why should we not say instead that all states of consciousness are privative derivatives of unconsciousness? More plausibly, could not unconsciousness come in degrees instead of consciousness coming in degrees? Could we not generate states of consciousness by adding several powers – experience, reason etc. – to the zero state of unconsciousness rather than in the direction of deleting powers, as O’Shaughnessy suggests?
There are three negative properties of consciousness. Firstly, it has no object. This is shown by the contrast between `he was conscious’ and `he was conscious of a faint rustling’. Only in the latter usage is there an object. Consciousness proper figures only in the former usage and there it is more the arena for experience.
Secondly, it does not have mental origins. Consciousness arises in the brain and whether it is present or not is decided by the brain and not by us or our judgment – since we have no choice about whether we become awake or not, short of setting an alarm clock. We may likewise have some choice about whether we become unconscious in that we can try to stay awake, but only for a limited period. O’Shaughnessy uses this to argue against consciousness having mental origins, presumably because he thinks that the mental is the location of our choice and judgment, and because he thinks that the mental is not the brain.
Thirdly, consciousness is not an experience – for similar reasons to those used to argue that it has no object. This is true despite the fact that consciousness may inevitably be accompanied by experience.
What can we learn about consciousness by asking what are its minimal requirements? Consider the simplest possible conscious animal. It does not seem to need any motor or perceptual capacities in order to be conscious; all the requirements for consciousness are internal. There must however be attentive experience which generates beliefs about the environment. We do not need to ask how this could occur without perceptual systems, because the key criterion for consciousness is cognitive sensitivity to perceptual experience. This means something can be conscious if it would respond to perceptual input about the environment in the right way, were there to be any. While this looks implausible, it must be true unless we wish to deny that persons in sensory-deprivation tanks are conscious.
There is a contrast between the normal state of consciousness and that which obtains when dreaming. O’Shaughnessy diagnoses this as relating essentially to awareness of time. In particular, normal consciousness requires the capacity to perceive events across time.