Descartes applied illusion argument, dreaming argument, and evil genius argument that is called “method of doubt” to achieve his goals: Mind and body are two different substances, the complete separation of the mental world and the physical world.
Once, he claims that even awake or asleep, two plus three is always five. Even evil genius fakes us, we probably think two plus three is four but in fact it always exist as five and it is always true. Lets look at this example: If I think that it’s sunny outside, I can be wrong about sun but I cannot be wrong about my thinking that it’s sunny. So, no matter if I am being deceived or dreaming either way I am thinking, which is certain knowledge. Even though our senses aren’t reliable, when we see things we still have the experience of seeing that thing. Even if in a dream, an apple is still experienced as our definition of an apple. An apple in a dream will be still looked and smelled the same as an apple to us in a wake because the experience is the same. Because we really don’t definitely know if we are awake or asleep at any time we can only say that the experience of the apple is certain in our minds. For example while one is in deep sleep we do not know whether we are thinking or not. When we wake up we may remember a dream or two but when we think about it they may only add up to about five minutes in length even though we know we were asleep for eight hours. There is all of that time when we don’t remember what we were thinking or if we were even thinking at all. When using this argument as an objection to the “I think, therefore I am” we say that it is impossible to not be thinking because to stop thinking is to no longer exist. Descartes would say that even though we may not remember that we were thinking, we were thinking nonetheless. There are many things which we don’t remember. I don’t remember being born but that does not mean that I wasn’t thinking at the time. During the night we might be woken up by a loud sound, but after we wake up we might not remember a thing. It still remains that even though we can’t remember any thought before we wake, we know that there was because we heard the noise and woke up. We still have experiences while asleep whether they are dreams or experience of hot or cold or a smell or a sound. We know we still experience them because they arouse us to wakefulness and therefore are experience while in deep sleep. Therefore, it is possible that while in deep sleep we might not remember everything we thought but we are still thinking or else we would probably never wake up. Think about how you wake up at any time and it is obvious that some thought is involved. And the wakefulness by loud sound or disturbance is also called reaction but not the interaction of body and mind.
Mind is conscious and non-spatial and body is spatial but not conscious. While separate, these two substances interact. The mind, which can’t be doubt or divided or extended, no shape but it is to think in the pursuit of knowledge and the body, in return, can be doubt, divided, extended, occupied space, is a place containing brain that generates thought.
Descartes asserts that the mind and body are separable and infinite by using his method of doubt to show that he could not doubt the existence of his mind. As long as we think, we are existing because we must exist first then to think. As doubting involved thought, and thought needs a consciousness to think it, Descartes was sure that he could not doubt his mind existed: “I think therefore I am”. He claims to know what a thinking think is, and he regards we are as thinking thing.
The Cartesian Dualism is still having problem of explanation of how mind and body interact or why mind does not stuck in body or mind control body. Insisting that the mental representation does not represent the physical is very confused and does not completely explain the issues. Descartes insists that God is responsible for these interactions and only He knows how the process works. So, reaction is the interaction between mind and body? The answer is “no”, because reaction is happened before we think what we should do. Therefore, mind does not control completely body but partial of it.
Descartes agrees that the mind, characterized by mental substance, and the body, characterized by physical substance, are separable and immortal. However, Descartes questions whether the physical body even really exists at all. Although these philosophers do not have a clear understanding of how the mind and body, which are separate entities, interact, they clearly agree that mental and physical are separable and immortal.