5.1.2.1 Descartes and Dualism

Rene Descartes’ principle of Dualism divided the universe into thought and all other external entities. In his philosophy, there is an external world, but humans are separated from it by an unbridgeable gap. We really know only what is in our own consciousnesses, which divides us from that world. We are immediately and directly aware of only our own states of mind. Because of this, all of reality is reduced to an idea or picture in our minds. Therefore, it is possible to doubt the reality of the external world as consisting of real objects.

This is the problem/paradox with Cartesian dualism – if we are only aware of our mental states, how can we be sure they represent anything outside our minds? Although Descartes didn’t solve this problem, many who came after him have provided convincing arguments that appear to overcome his doubts. Brentano’s theory of “directed attention”, Moore’s proof of reality, Wittgenstein’s, Moore's, and Russell's dismissal of many philosophical problems as word games and misuse of language, Correspondence theories of reality, coherence among the difference sciences, and Logical Positivist overall dismissal of this as even an interesting problem make it hard to take Descartes doubts seriously as they once were regarded.

Descartes started his investigation by doubting everything except his own thought process, and then tried to re-establish and derive everything else from that. Whether or not that was a wise starting point is not universally agreed upon (for example, the Pragmatists only chose to doubt concepts that seemed doubtful, reality not being one of them). Despite his doubts, though, Descartes was convinced that our conception of reality was close to being correct. The purely Rational (i.e., deductive) process he used to arrive at this conclusion started with an ontological proof of God’s existence, along with a proof that God is good. Ontological proofs of this type have since been severely criticized by Hume, Kant and others and shown to be structurally flawed, though they continue to be used occasionally even today. Anyhow, according to Descartes, because of God’s demonstrated benevolence, we can trust the account of reality provided by our senses. God created the world, and He gave us functioning minds and reliable sense organs. He would not attempt to deceive us and would never engage in such a malicious deception. This would be incompatible with his fundamental goodness. Therefore, what we perceive really exists.

Interestingly, Evolutionary Philosophy uses a modified form of this same argument. In that view, it is not God who gave us reliable sense organs, but natural evolutionary processes. This is covered more completely in a later section.

So, he initially only accepted the reality of the mental realm and doubted physical reality, along with everything else. However, at the end of his analysis, Descartes comes down on the side of the realists, in that he believed he proved that there was an external reality and that there was no reason for us to doubt what we were seeing really existed.