Before we are able to consider whether or not it is an advantage of Descartes substance dualism that it allows the possibility of life after death, we must first grasp the notions at hand in order to digress further in our understanding. For this reason a brief account of dualism shall precede the main argument. Dualism is the theory which holds that the mind and body, while intimately connected to each other, are at the same time distinct in themselves. When referring to the 'mind' Descartes included in its definition any sensation that he could not locate physically.
The mind determines our personality while the body is an outer shell for the real self. Descartes believed that the body will eventually die and decay as it is contingent but the mind or soul is immortal and so can survive the death of the body and enter into eternity. This is made clear when he writes: "The soul is of a nature wholly independent of the body, and that consequently it is not liable to die with the latter and, finally, because no other causes are observed capable of destroying it, we are naturally led thence to judge that it is immortal. (Descartes Ch. 5).
A group which may discredit Descartes dualism because it allows for life after death are religious non-believers. They may have supported his reasoning about the mind and the body as being distinct from one another but the idea of life after death may be too far-fetched for some to support. In order for our souls to leave our bodies it suggests that at some point they must have been put inside them. The question then arises as to who, if anyone, has done this, why it is so, where will they go next etc.
According to Descartes God has created our souls but if he has done so, then when has he done this and would this not make them contingent and therefore not everlasting? Descartes states that "... no other causes are observed capable of destroying it... it is immortal", so we are led to believe here that the lack of evidence proves that there is a life after death. If we took this approach it seems as though it does quite the opposite.
The non-believer may argue that since there is no proof of a soul then it must be concluded that it, and therefore life after death, does not exist. While non-believers may argue the previous points, believers are just as inclined to oppose them and support Descartes. Although beliefs such as atheism and agnosticism are gaining popularity and people assume that religion is losing support it is shown that many, if not most, people in the world still believe in a higher power.
With so many followers of religion, and in turn life after death, it could be seen as though the inclusion of life after death is beneficial in Descartes' substance dualism. If one argues that there is no proof of the soul then the believer may state that faith alone is proof that there is a soul and such things as the Bible, Torah and Quran help to develop that faith. However, these views can be easily discredited as being mythical rather than factual but then there are cases when non-religious people have undergone experiences which have made them believe that they have a soul.
There are some people who have had a near death experience where, even after their heart had stopped beating, they felt themselves leave their bodies and some have even seen their own lifeless bodies on the operating table. These people, being unconscious, would have had no way of knowing their surroundings, yet afterwards they realise that the images they had whilst their heart had stopped beating was an exact description of what their surroundings were like in reality.
This belief in life after death shows that a lot of people still support the idea of the soul and so may be influenced to support Cartesian Dualism. Gilbert Ryle, in his book The Concept of the Mind brought forward the idea of 'the ghost in the machine' in which he stated that the concept of the soul was a mistake in the use of language . He pointed out that when people distinguish between the soul and the body they see the soul as something identifiably extra.
Ryle uses the analogy of a foreigner asking where the team spirit is at a cricket game, as he expected it to be something separate from the field, players and umpires etc. However, team spirit is of course not a separate thing from the game but a collection of the behaviours of those involved in it. Like this Ryle believed that the soul is in fact another way of defining the way in which different people integrate with each other and that having such character traits as being generous, intelligent or pessimistic does not necessitate the existence of a soul.
He argued the point that when you buy a pair of gloves you can say that you have bought a left-hand glove and a right-hand glove but not that you "had bought a left-hand glove, a right-hand glove and a pair of gloves" (Ryle, p. 89) and so it is the same mistake when talking of the mind, body and soul. It could be argued that while the mind and body may be separate there is nothing to say that the soul does not die with the body. Dualists will not refute the fact that the mind and body are connected but then the question arises as to how far we can take this connection.
Descartes himself saw the mind and body as "... very closely joined, and as it were, intermingled" (Rosenthal, p. 26). If we take the example of Siamese twins, in many instances it is the case that if one twin dies then so does the other because they are dependant on each other. The mind and body seem to be closely combined so does this union not suggest that both cease to exist together? One of Descartes counter-criticisms is the fact that if one were to lose say an arm then "... nothing has thereby been taken away from the mind. " (Rosenthal, p. 28).
However one could take the view that something has in fact been taken away from the mind; the experiences one would have had with the limb which is now missing. You may have memories of using the arm but you would never have another mental process of you actually experiencing it again and so in a way those experiences disappear from the mind; they could even be said to die. If we apply this logic to the whole body then we could come up with the view that when one's body dies then so do their experiences of that body. All experiences of life may leave the body when it dies along with the mind or soul.
This somewhat more realistic view of dualism may be a disadvantage of Descartes' dualism that it allows for life after death because it appeals to those who may not believe in a higher power. Descartes arguments for the existence of God can be easily criticised and so it may be seen as illogical to come to any conclusion about the soul and life after death from such an unsteady foundation. When attempting to prove something, those who are being persuaded will often ask for proof. There is little evidence to prove life after death and so why would someone think that the soul can survive the death of the body?
It may be understandable to believe that it did if, say every so often, our souls decided to leave our bodies and go off on their own to experience the world. This is of course not the case for most people. Our minds seem to be dependant on our bodies. Although people may like to think that looks are not important in this day and age, it is clear that everyone is different and so the way the body looks is just another factor which makes us that way. From this it may become apparent that the soul is changing constantly just as our bodies are.
When a person reaches their twenties their bodies are completely different from when they were say five years old. Every single cell of the old body has now died and been replaced by new cells and so physically it is like they are two completely different people. In terms of change mentally, this person should now have matured and it is doubtful that he still has the same thoughts and beliefs as he did as a child and so it is evident that the mind keeps changing along with the body. So from birth the mind and body work together and through life they mature together and so ultimately should they not die together?
Going back to the original question as to whether it is an advantage of Descartes' substance dualism that it allows the possibility of life after death it would appear that it depends on who he is trying to persuade. A religious person may think that it is an advantage while a secular person may think the disadvantages outweigh its advantages. When putting religion aside and attempting to study his theory with an open mind one may observe that Descartes arguments about dualism are strong and quite plausible. However, when discussing life after death his arguments seem to fail.
When answering objections which have been put before him, he does on the one hand make outright claims about the mind and body but then he appears to use God as a scapegoat and makes the claim that "God alone can reply" (Descartes, p. 84). This is similar to his whole theory of dualism. At the beginning his reasoning appears to be sound about dualism but then, when he introduces life after death, he appears to take an inductive leap which does not fit in with his earlier rationality. For these reasons it looks as if the allowance of life after death is a disadvantage to Descartes substance dualism.