By Mano Singham
In the model of Cartesian dualism, we think of the mind as a non-material entity that interacts somehow with the material brain/body in some way. Descartes thought that the locus of interaction existed within the pineal gland in the brain but that specific idea has long since been discarded.
But that still leaves the more fundamental idea, referred to now as Cartesian dualism, that states that I do have a mind that represents the essential 'me' that uses my material body to receive experiences via my senses, stores them in my memory, and orders actions that get executed by my body. This idea that there is an inner me is very powerful because it seems to correspond so intuitively with our everyday experience and the awareness that we have of our own bodies and the way we interact with our environment. Even the way we use language is intricately bound up with the idea that there exists some essence of ourselves, as can be seen by the way the words 'we' and 'our' was used in this and the previous sentences. The power of this intuitive idea of something or someone inside us controlling things has resulted in phrases like 'the ghost in the machine' or a 'homunculus' (from the Latin for 'little man') to describe the phenomenon.
For religious people, the mind is further mixed up with ideas of the soul and thus gains additional properties. The soul is considered to be non-material and can exist independently of the body, allowing for the possibility of an afterlife even after the body has ceased to exist. This soul model causes some problems that resist easy answers. For example, life begins with the creation of a single fertilized egg. This single fertilized cell (called a zygote) then starts to multiply to 2, 4, 8, 16 , 32,. . . cells and so on. All these cells are material things. At what stage along this progression did a non-material entity like the soul appear and attach itself to the collection of cells?
I think it is safe to say that almost all cognitive scientists reject the idea of a non-material mind, some kind of homunculus inside the brain somewhere that 'runs' us. This immediately rules out the religious idea of a non-material soul, at least in any traditional sense in which the word is used.
But even though the existence of a non-material mind or soul has been ruled out, the Cartesian dualistic model is still a seductive idea that can tempt even those who reject any religious ideas and accept a framework in which the material body (and brain) is all there is. The reason it is so seductive is that even if we discard the mind/body distinction as being based on a nonmaterial/material splitting, the idea of a central processing agent still seems intuitively obvious.
Consider a situation where I am responding to something in my environment. We know that we experience the external world through our five senses (sight, sound, smell, touch, taste) and that these senses are triggered by material objects coming into contact with the appropriate sense organs (eyes, ears, nose, skin, tongue) and excite the nerve endings located in those organs. These excitations are then transmitted along the nervous system to that part of our brains called the sensory cortex after which they…what?
At this point, things get a bit murky. Clearly these signals enter and proceed through our brain and excite the neural networks so that our brain becomes 'aware' of the phenomena we experienced, but the problematic issue is what exactly constitutes 'awareness.'
Suppose for the moment we stop trying to understand the incoming process and switch to the outgoing process. It seems like we have the ability to make conscious and unconscious decisions (pick up a cup or shake our head) and then the brain's neural networks send these signals to the part of the brain known as the motor cortex which transmits them to the appropriate part of the nervous system that sends the signal to the body part that executes the action by contracting muscles.
It seems reasonable to assume that in-between the end of the incoming pathway and the start of the outgoing pathway that I have described that there is some central part of the brain, a sort of command unit, that acts as a kind of clearing house where the incoming signals get registered and processed, stored in memory for later recall, older memories and responses get activated, theories are created, plans are made, and finally decisions for action are initiated.
As a metaphor for this command unit, we can imagine a highly sophisticated kind of home theater inside our brain where the screen displays what we see, speakers provide the sound, and is also capable of providing smell and touch and taste sensations, and banks of powerful computers by which memories can be stored and retrieved and action orders transmitted. 'Conscious events' are those that are projected onto this screen along with the accessory phenomena.
Daniel Dennett in his book Consciousness Explained (1991) calls this model the Cartesian Theater and warns against falling prey to its seductive plausibility. Accepting it, he points out, means that we are implicitly accepting the idea of a homunculus, or ghost in the machine, who is the occupant of this theater in the brain and who is the inner person, the 'real me' and what that inner person experiences is sometimes referred to as the 'mind's eye.' One problem is that this approach leads to an infinite regress as we try to understand how the Cartesian Theater itself works.
But if this simple and attractive model of consciousness is not true, then what is? This is where things get a little (actually a whole lot) complicated. It is clear that it is easier to describe what cognitive scientists think consciousness is not than what they think it is.
More to come…