The Unity of Consciousness
I have maintained that a key feature of rational inference is that it is inference that must be performed by an agent who possesses a unified consciousness. The idea is that if the self-same entity does not think the premises and think the conclusion, then we have no rational inference. If Dennis has the thought “All men are mortal,” and Bill has the thought “Socrates is a man, and I have the thought “Socrates is mortal,” then none of us have preformed a rational inference.
Now, I have quoted some naturalistic thinkers, such as Blackmore and Pinker (and Dennett seems also to be in this category) who deny the unity of consciousness. The unity is the result of some sort of a user illusion. But if the unity is an illusion, isn’t the inference as well? Or so I would have thought.
Perhaps I can begin discussing the argument by seeing how it appears in Immanuel Kant. Kant seemed to perceive this as a successful argument against materialism but not as an argument in favor of a simple soul, and this is because his own solution to these philosophical problems was to rely on a distinction between the self as it appears to us and the self as it is in itself. But Kant develops the argument as follows:
Every composite substance is an aggregate of several substances, and the action of a composite, or whatever inheres in it as thus composite, is an aggregate of several actions or accidents, distributed among the plurality of substances. Now an effect which arises from the concurrence of many acting substances is indeed possible, namely, when this effect is external only (as, for instance, the motion of a body is the combined motion of all its parts). But with thoughts, as internal accidents belonging to a thinking being, it is different. For suppose it be the composite For suppose it be the composite that thinks: then every part of it would be part of the thought, and only all of them taken together would be the whole thought. But this cannot consistently be maintained. For representations (for instance, the single words of a verse), distributed among different beings, never make up a whole thought (a verse), and it is therefore impossible that a thought should inhere in what is essentially composite. It is therefore possible only in a single substance, which, not being an aggregate of many, is absolutely simple.
William Hasker, the argument’s chief contemporary architect, has a version of the argument that has been formalized as follows:
1. I am aware of my present visual field as a unity; in other words, the various components of the field are experienced by a single subject simultaneously.
2. Only something that functions as a whole rather than as a system of parts could experience a visual field as a unity.
3. Therefore, the subject functions as a whole rather than as a system of parts.
4. The brain and nervous system, and the entire body, is nothing more than a collection of physical parts organized in a certain way. (In other words, holism is false.)
5. Therefore, the brain and nervous system cannot function as a whole; it must function as a system of parts.
6. Therefore the subject is not the brain and nervous system (or the body, etc.).
7. If the subject is not the brain and nervous system then it is (or contains as a proper part) a non-physical mind or “soul”; that is, a mind that is not ontologically reducible to the sorts of entities studied in the physical sciences. Such a mind, even if it is extended in space, could function as a whole rather than as a system of parts and so could be aware of my present visual field as a unity.
8. Therefore, the subject is a soul, or contains a soul as a part of itself.
Now people on the Internet Infidels Discussion Board have been trying to persuade me that my brain can experience my visual field, or the diachronic experience of rational inference, as a unity. The brain, they say, is closely interconnected functionally, and has billions (and billions) of neurons. But I guess I just have to ask them whether they think holism is true, or not. Are physical systems the sum of their parts. If so, then the properties of the “whole” have to be summative properties of the parts. Tell me where all the red bricks are, and even without using the word wall, I can know that there is a wall over there. The properties of the wall are entailed by the properties of the bricks. Wallness is a summative property of bricks. Intentionality and the unity of consciousness do not seem to be entailed after you add up all the properties of the proper parts of the brain. This will be controversial, but I’m prepared to argue that if you add up all the physical states of a person, you could still end up with a zombie.