Most people are probably familiar with dualism. It is the claim that the mind exists as an immaterial substance. It is often called “Cartesian Dualism”, because of the way that it was formulated by Descartes. However, the idea of a spiritual soul seems to be much older.
Apparently, Descartes was familiar with the workings of a clock, and saw that the kinds of mechanisms used could possibly explain motions and other visible behaviors of animals and people. But he did not believe that it could explain thinking. So he argued for two substances. The physical motions would be explained by extended stuff (or material substance), while thought would be explained by thinking stuff (or mental substance), taken to be distinct from extended stuff.
Modern views
Since the time of Descartes, much has been learned about anatomy and about the brain. And our experience with computers shows how intricate behavior can be controlled without requiring any immaterial substance. As a result, dualism is now rejected by many people. However, many religious folk still like the idea of a spiritual soul, so continue to cling to some kind of dualism.
These days, most people of a scientific bent point to the brain as responsible for what Descartes attributed to an immaterial mind. And most academic philosophers agree, though there seem to be a few holdouts.
Passive perception
Descartes took the view that perception is passive. That is, we just perceived the world the way that it actually is. This seems a reasonable conclusion for a dualist such as Descartes. If the mind was assumed immaterial, it could do magical things.
We are now in an era where dualism is widely rejected. Yet many people still take perception to be passive. I am inclined to see this as a residual dualism.
Perception is quite complex, and computers cannot really do it. If we want our computers to be able to recognize a can of soup, we print a UPC bar code on the label and design computer to scan for that bar code. And then they can look up the code in a database to identify the item. This is not at all like the way that humans do it.
Attempts at computer vision are often based on Marr’s theory of vision (a web search will return a lot of information). It is a theory based on geometry. When trying to implement a computer vision system this way, the computer scientists find that a lot of innate knowledge must be programmed into the computer. I am skeptical of that.
For example, I grew up in Australia, and had no difficulty recognizing a kangaroo when I saw one. Yet, if I go back more than a couple of generations, my ancestors were from Europe where there are no kangaroos. If recognizing kangaroos requires innate knowledge in the genes, it is difficult to explain how it could get there.
I’m inclined to think that perception is far more creative than could be allowed by the idea of passive perception.
Truth
I have a similar issue with truth. People seem to think that truth just exists. Religious folk say that it comes from God. Others really cannot say where it comes from. I’m inclined to also think of that as a residue of dualism.
My own view of truth, is that it comes from the community, as I discussed in some earlier posts on truth. As far as I can tell, there is no external source of truth.
Summary
In summary, it seems to me that although many people have rejected dualism, there are still remnants of dualism in our thinking.
The Heretical Philosopher 