In the sixth installment of Descartes' Meditations on First Philosophy, he claims that mind and body are distinct. My objective in this paper is simply to present the argument and explain how he arrives at the conclusion. Additionally, I will offer an objection to Descartes’ argument. Specifically, I will consider Princess Elisabeth’s concern regarding the causal interaction of mind and body. Before moving forward with the argument set up and analysis however, I would like to offer a clarifying definition and expand on how the understanding of this definition is paramount to the understanding of the argument.
In Meditation One Descartes decides it necessary that we remove all ideas/thoughts that leave room for doubt and treat them as though we know them to be false (41). This "method of doubt" is employed to discover what we really know, "clearly and distinctly", which I interpret to mean that which is self-evident and cannot be doubted. Clear and distinct ideas are reliable and are beyond reason for doubt because they are not obtained through our senses, which can be deceiving (wax example, 45). Rather, these are ideas that come from God and therefore cannot be false, "I acknowledge that it is impossible for God ever to deceive me, for trickery or deception are always indicative of some imperfection (45)." God cannot deceive us, he is in all ways perfect and infinite in knowledge and it would be uncharacteristic of him to deceive. So, from this, we can go on to identify principles that will support the mind-body distinction argument in the final meditation.
Now, I will restate the argument. Premise one: God can create anything that I clearly and distinctly perceive. God can create that which we can know beyond reason of doubt. That which we can know beyond reason of doubt is to be trusted, because as previously stated, God will not deceive, and God has created the things which we perceive. In the Fifth Meditation he states, "But once I perceived that there is a God, and also understood at the same time that everything else depends on him, and that he is not a deceiver, I then concluded that everything that I clearly and distinctly perceive is necessarily true (61)." The success of the argument depends heavily on this premise, given that everything that follows relies on accepting that clear and distinct ideas can be trusted to be true. Premise two: If God can create something that can exist without the other, they are distinct. Because we can conceive of God creating X without the necessary existence of Y, then X must not depend on the existence of Y for its own and therefore are distinct.
Premise 3: I clearly and distinctly perceive I am a thinking thing. Here I refer back to Meditation Two, "I am therefore precisely nothing but a thinking thing; that is a mind… (44)." Being a thinking thing is what one is, it is the inherent nature of a human, its essence. For further clarification, Descartes describes a mind as being a substance, that which does not depend on something else for its existence. Premise 4: God can create a thinking thing independent of a body. In Premise 2 we have already acknowledged the possibility of the X existing without reliance on Y's existence. It follows then that a mind (X) can exist without a body (Y). A thinking thing doesn't depend on the existence of a body for its own existence.
Premise 5: I clearly and distinctly perceive of a body as an extended thing and not a thinking thing. A body, unlike a mind, is that which is extended, can be measured by length, breadth, and depth (58). Descartes states that bodies haven't been fabricated by him, but that they have "their own true and immutable nature (58)." Descartes uses the example of a triangle to show that even if it didn't exist outside of his mind it would still have measurable extension, a form which is unchangeable, three angles that are equal to two right angles for example (58). The final Premise: God can create a body independent from a mind. As previously stated, the triangle exists independent of the mind, this is the case for any body; lines, shapes, solids, gasses, liquids, etc., they exist though they are not thinking things.
This series of premises leads Descartes to conclude that the mind is distinct from the body. The mind and body are distinct because they have different properties. A mind thinks, affirms, denies, while a body is an extended thing with dimensionality. Yet, his argument, however methodical, has been met with various objections. I will now address one of the objections and offer a possible way that Descartes would have responded. Princess Elisabeth of Bohemia who corresponded with Descartes raised some concerns in her letters. In one of her letters, she asked, "…please tell me how the soul of a human being (it being only a thinking substance) can determine the bodily spirits, in order to bring about voluntary actions (62)." In other words, she wanted him to explain how the soul or the mind causally interacts with the body in order to bring about physical action. This is a reasonable concern to have.
Take fear, for example, fear is an idea existing only in the mind and yet can have very noticeable effects on the body. In situations where people are fearful they may notice their heart rate speeding up, they may sweat, get nauseous, their muscles may tense up in a fight or flight response. Even more so, people who have previously experienced trauma may show signs of PTSD, a disorder where physical responses may be triggered by thoughts or memories of the trauma. How is it possible for something physical to be affected by something immaterial?
What is the explanation for how ideas or thoughts can cause physical actions? What process takes place that allows the mind to move the body? Descartes responded that she had confused the way the mind acts on the body with the way a body acts on a body. He appeals to real qualities like that of heaviness. In the same way that heaviness explains why a rock falls to the ground, the mind moves the body.
He later goes on to state that the things that make mind and body distinct are being used in an attempt to explain their causal relation. But to make it easier to understand she should, "feel free to attribute this matter and this extension to the soul, for to do so is to do nothing but conceive it as united with the body (74)." In short, he's encouraging her to attribute the properties of bodies to the soul in order to understand how the mind is united with the body. But this does not solve the problem, conceiving of the soul as extended still does not explain the causal interaction between mind and body. Furthermore, it leaves open the question of how a body can affect the mind. The body has sensations like hunger, pain, or pleasure which influences our thoughts.
While Descartes argument to prove the distinction of mind and body may be a valid one, his inability to concretely explain what process takes place that allows for cross interaction makes it difficult to accept. If mind and body are really distinct it should be explained not only by them having different attributes but by how these attributes interface with each other. For a moment, let us equate the mind with electricity, and the body with an appliance. We can understand that the electricity behind a wall socket persists even if there is nothing plugged into it. We understand that the appliance will continue to exist independent of whether its receiving power from the electricity. In this example, however, we understand that when the appliance is directly connected and interacting with the electricity it is being powered, it is able to function, it is “moving”. Descartes fails to make such a connection.