Essay: Consciousness

Our experiences of different types are distinct yet, they don’t seem to be disunified. Prima facie, consciousness is unified. Yet, to account for the unity of consciousness, there seems to be at least two questions to be answered first: What form of mental unity is essential for consciousness to be unified and how unified conscious experience is structured. That being said, what I want to do in the paper is to figure out whether the unity thesis is true or not. Hence, the paper will consist of three parts: the unity thesis (Bayne and Chalmers, 2003), the split-brain syndrome and its implications for the unity thesis (Sperry, 1968 and Nagel, 1971 respectively) and responses from Bayne (2008).
As Bayne and Chalmers pointed out there are at least three possible claims to be made: the unity of consciousness is necessary, the unity of consciousness can be broken down and the unity of consciousness is usually disunified. They argue that necessarily, ‘any set of conscious states of a subject at a time is unified’ (2003, p. 2). Then, they distinguish different notions of unity and those are objectual unity, spatial unity, subject unity, subsumptive unity, access unity and phenomenal unity. I will only explain subsumptive unity, phenomenal unity and access unity in depth because ultimately, the consciousness they are concerned here is phenomenal consciousness and accordingly, the unity that is relevant here is phenomenal unity and since they will use access unity in order to account for the split-brain syndrome, access unity is also relevant here.
So, consider the following for brief explanations of these notions of unity. Objectual unity is a matter of states being directed at the same object. They discuss how objectual unity needs a solution of binding problem but as I have said, it is not my concern here, at least at this point so, I will leave that discussion out even though it is of value. Spatial unity is a matter of states representing objects as being part of the same space. Subject unity is a matter of states being had by the same subject at the same time. I would like to point out that according to them, subject unity is trivial but they might have a false assumption there since forming or identifying the set of all phenomental states had by subject S at time t might be problematic after all. Subsumptive unity is a matter of two or more states being subsumed within a state of consciousness (2003, p. 3-5). Then, they state that there exists a total conscious state for S, if all of S’s phenomenal states at t is subsumed by a single phenomenal state. It is important to say that this total state is not a mere conjuction of the states because it is a state itself. Later on, they clarify that because of the relation of subsumption is reflexive, regress is not an issue here (2003, p. 21).
After that, they adopt Ned Block’s distinction between access consciousness and phenomenal consciousness according to which a mental state is access conscious when S can access to the content of the mental state and a mental state is phenomenal conscious when there is something it is like to be in that state. So, if conscious state A has the content p, A is access conscious if S can access the information that p for report and control. Access consciousness and phenomenal consciousness are subsumptive as well. Hence, two or more states are subsumtively phenomenally unified if there is something it is like to have all of the states together and similarly, two or more states are subsumtively access unified the conjunction of the states in question is accessible. Even though I am not sure whether they actually make the claim but it looks like they are making a negative claim that subsumtive phenomenal unity is about mereology whereas subsumtive access unity is about conjuction. If so, subsumtive phenomenal unity requires a solution for the problem of how states are combines into a single state, which is known as the combination problem (2003, p. 6-15).
Now if we go back to the unity thesis, one will inclined to say that it is a truism that if one is a subject then, necessarily, one’s mental states are phenomenally unified. Indeed, some of the philosopher took the unity thesis granted. One example would be Descartes since he uses the unity thesis as an intuitive premise to the argument that mind is not physical. He argues that anything physical must have parts but mind, or ‘I’ as a think thing, do(es) not have parts because mind is clearly one and entire thing. Hence, he says that the unity thesis itself is enough to prove that dualism is true. Yet, with the split-brain syndrome some philosophers suggested that consciousness can be broken down. As counter-intuitive as it may seem this claim has its own appeal. Before the discussion of the claim that consciousness is not necessarily unified, consider the following explanation of what split-brain syndrome is. In 1960s, It was thought that by severing the connection between the left and the right hemispheres of the brain, at least certain types of epilepsy could be inhibited. Sperry was working with subjects who suffered from epileptic seizures and after the procedure, patients lived a relatively easy life. However, they also reported they were experiencing some odd behaviours. These behaviours were related to unifying sensory input which are later on explained by attributing them to one hemispere or the other. Sperry conducted split-brain experiments in which two stimuli were presented to the subject in a way that one of the stimuli was processed by the left hemisphere and the other stimulus was processed by the right hemisphere. To sample, the words ‘key’ and ‘case’ were presented in a way that the word ‘key’ was projected to the left visual field and the word ‘case’ was projected to the right visual field. Hence, the word ‘key’ was processed by the right hemisphere and the word ‘case’ was processed by the left hemisphere (Sperry 1968, p. 723-725).