The Cartesian Theater

 Normally we feel that we perceive the world from a location behind our eyes. We assume that our “self” resides somewhere behind our eyes.

This idea is called “The Cartesian Theater”. Our “self” sits somewhere inside our head and sees through the eyes of the body “host”. The problem of this idea is that it needs to explain how the “self” inside the head can see the “movie”. That requires another host inside the first one inside which we claim that the “self” exists. Upon questioning this second host, a third one is made where the “self” is claimed to exist and so on. This is called infinite regress and in a universe with physical limits it seems very unlikely.

During Out of Body Experiences, subjects claim to have their “self” moved outside of their body. And some claim that this proves the existence of some metaphysical “essence” that is called “soul”.


Greg Egan’s short story Seeing is about altered states of consciousness (ASC), out-of-body experiences (OBE) in particular. The patient suffers a constant and  uninterrupted experience of OBE as a result of brain damage. The point of view of his “self” moves from the location behind his eyes to somewhere outside and above his body. He “sees” the world from a location above his body and when his body moves, “he” moves accordingly. Testing his claimed ability to see things from a location above his body, medical staff display a whiteboard with shapes and letters to “him above” while not showing it to “his body”. He fails to guess most of the stimuli shown to him. But when the test is reversed and only “his body” sees the stimuli, he succeeds in recognising the visual stimuli. The conclusion of the tests is that”he” can only see what his eyes see.

Much of Seeing revolves about the patient trying to make sense of the fact that the way he perceives the world is an illusion caused by damage to his brain. He notices that his expectations of his perception of sounds relative to his position is constantly inaccurate. Whenever the eyes of his body are covered, “his sight” is covered as well. Even though he is in a well-lighted room, the only things he can accurately see are those that his body lying in bed looking upwards can see. He “sees” other things (i.e. like the position of a book right outside of his “body’s” field of vision but he soon realises that they are things that he expected to be rather than things that actually exist in the way he perceives them. There is a nice explanation about visual perception and how dependent it is on previous memories, expectations, etc.

Concluding thoughts

Do we see what is there?

The end product of visual perception is not a movie in your head, it’s a set of visual conclusions about the world.