2.1.1: Descartes

  1. I find in my mind the idea of a perfect being.
  2. The cause of my idea of a perfect being must have at least as much perfection and reality as I find in the idea.
  3. I am not that perfect.
  4. Nothing other than a good and perfect God could be the cause of my idea of a perfect being.
  5. So, a good and perfect God must exist.

This argument simplifies the rather involved reasoning Descartes goes through in the Meditations. But it will do for diagnosing the fatal flaw in Descartes’ reasoning. Let us grant the validity of the argument and consider the truth of its premises. Keep in mind that to accord with the method Descartes has set for himself in carrying out a rational reconstruction of well grounded certain knowledge, all of the premises of this argument must be indubitable and foundational. Being a belief about the contents of his own mind, we can grant the certain truth of premise one. Though it is not as clear, premise three might arguably count as a foundational belief about the contents of Descartes’ own mind. An evil deceiver, being evil, would lack perfection found in Descartes’ idea of a perfect being. So as powerful as such a being could be, the cause of Descartes’ idea of a perfect being must be more perfect than any evil deceiver. Perhaps any being so perfect would have to be a good God.

But the fatal flaw for Descartes’ rational reconstruction of knowledge is the second premise. What are our grounds for thinking that the cause of something must have at least as much perfection as its effect? The idea of degrees of perfection and the notion that the less perfect can only be explained in terms of the more perfect is an idea that we find in Plato’s theory of forms. It will strike many of us as implausible or even incomprehensible. Just what is perfection supposed to mean here? And even once we’ve spelled this out, why think causes must be more perfect? It seems not at all uncommon for less perfect things to give rise to more perfect things (just consider my son, for instance). In any case, whether the second premise can be explained and defended at all, the fatal flaw for Descartes’ project is that it is not foundational. It is not an indubitable belief about the contents of Descartes’ own mind, but rather a substantive belief about how things are beyond the bounds of Descartes’ own mind. So Descartes’ attempt to provide a rational justification for a substantive body of knowledge leaves us with an enduring skeptical problem. All we have immediate intellectual access to is the contents of our own minds. How can we ever have knowledge of anything beyond the contents of our own mind based on this? This is the problem of Cartesian skepticism.

Having diagnosed the fatal flaw in Descartes’ project, we should briefly consider how his rational reconstruction of knowledge was to go from there. Given knowledge of God’s existence and good nature, we would appeal to this to assure the reliability of knowledge had through reason and later also through the senses. God being the most perfect and good being would rule out the possibility of interference by an evil deceiver. We might still make mistakes in reasoning or be misinformed by the senses. But this would be due to our failure to use these faculties correctly. A good God, however, would not equip us with faculties that could not be trusted to justify our beliefs if used properly. This is a very cursory summary of the later stages of Descartes’ attempted rational reconstruction of knowledge in his Meditations. But it will suffice for our purposes.

The mind-body problem

Descartes is a substance dualist. This is the metaphysical view that the world is made up of two fundamentally different kinds of substance: matter and spirit (or mind). In the Second Meditation Descartes motivates this view by arguing that there are distinguishing differences between the mind and the body. In particular, I can doubt the existence of my body but I can’t doubt the existence of my mind. Is this a difference that justifies denying that the mind is in some sense identifiable with the body? If something is true of one thing and not of another, then we have conclusive grounds for thinking they are not one and the same thing. So if my favorite bike is red but the bike in my office is yellow, then the bike in my office is not identical to my favorite bike. Does this straightforward line of reasoning apply to the case of the mind and the body? The existence of my body is dubitable, but the existence of my mind is indubitable. Descartes would count this as a reason for denying that my mind is identical with my body. But consider this analogous argument:

  1. Mark Twain is such that Joe thinks he is the author of Huckleberry Finn.
  2. Samuel Clemens is not such that Joe thinks he is the author of Huckleberry Finn.
  3. So, Mark Twain is not identical to Samuel Clemens.

Clearly the conclusion that Mark Twain and Samuel Clemens are not one and the same person does not follow in this case. As the Mark Twain argument looks like it is closely analogous to Descartes’ argument for the non-identity of the mind and the body, it looks like Descartes’argument is not valid. The problem here is that the premises of both arguments concern someone’s mental states about something. In Descartes’ argument we have premises about what he can or can’t doubt. In the Mark Twain argument we have premises about what Joe does or doesn’t believe. But people can fail to recognize true identity claims. Joe doesn’t know that Mark Twain just is Samuel Clemens. Because of this, Joe can believe one thing about Mark Twain and something different about Samuel Clemens. But this doesn’t show that Mark Twain and Samuel Clemens aren’t identical. Likewise, it may be that the mind is identical with the body or some part of it, but since Descartes doesn’t know this, he can believe one thing about the body (that its existence is doubtable) and something else about the mind (that its existence is not doubtable).

So far we have just offered a critical evaluation of one of Descartes’ arguments for mind/body dualism. Now we will consider a serious problem for the view. When Descartes’ considers how the substance of mind and body differ, he offers a view that should sound familiar from popular religious belief. On this view, the body is a physical object that exists in space and time and is subject to the laws of nature. The mind, being spiritual in nature, exists eternally in an abstract realm rather than existing in the physical realm of space and time. Further, the mind is not bound by mechanistic laws of nature, but it has free will that allows it to will or not will to do one thing or another. Descartes was both a believer in Catholicism and an active participant in the scientific revolution. He was among those who were developing a view of the natural world in which events occur in accordance with strict law-like regularities. A view of the natural world as functioning like a predictable clockwork mechanism was on the rise. And yet Descartes’Christian theology held that as a person created in the image of a divine being, he had free will through which he might choose to do one thing or another, perhaps most notably, to choose to accept the Catholic faith as true and be saved or not. His philosophical view is an attempt to reconcile these conflicting scientific and theological perspectives.

An unfortunate fact of history is that women in Descartes’ time were rarely given a thorough education or allowed to participate fully in intellectual life. A notable exception is the case of the Princess Elisabeth of Bohemia. And she was among the first to notice serious difficulties in the substance dualism that Descartes advocated. The central problem has to do with mind-body interaction. Clearly things going on in the physical realm have an influence on the mind. Light reflecting off clouds and trees cause me to have the mental perception of a sunset. And likewise, mental phenomenon cause things to happen in the physical world. When I mentally will to preserve the image of the sunset in a picture, my body causes things to happen in the law governed physical realm. I reach for my camera. But how can a non-physical soul be affected by or effect events in the physical realm? If events in the physical realm are all transfers of physical energy happening at specific places and times, how can it be that the non-physical mind has any role to play in this? The problem gets all the more difficult when we take the physical world to be deterministic, governed by laws where each event is determined to happen by prior events in conjunction with mechanistic laws. Determinism in the physical realm would appear to leave no room for the non-physical mind to influence events at all. Contemporary philosophers who study the nature of the mind generally take these problems to be intractable and to constitute decisive objections to Descartes’ substance dualism. More recent philosophy of mind has been mainly taken the mind to be physical. And philosophers, along with neuroscientists and cognitive psychologists, are making tremendous progress in understanding how mental phenomenon can be understood in biological, physical terms. When we take a closer look at more recent developments in the philosophy of mind, however, we will find some arguments for denying that some mental properties, consciousness in particular, can ever be identified with purely physical properties or processes.

Study Questions for Meditations 1-3

  1. Explain Descartes’ method of doubt. What is Descartes’ purpose in exercising this method?
  2. Why can’t Descartes be certain about beliefs he acquires through the evidence of the senses?
  3. Why can’t Descartes be certain about mathematical beliefs, like the belief that 2+2=4?
  4. What belief(s) does Descartes ultimately identify as indubitable?
  5. Why can’t an evil deceiver deceive Descartes about his belief that he thinks?
  6. How does Descartes build up from the foundation of indubitable beliefs?
  7. How does Descartes argue for the existence of God?
  8. Given the existence of God, how does Descartes justify his beliefs based on reason and on the senses?

This page titled 2.1.1: Descartes is shared under a CC BY-NC license and was authored, remixed, and/or curated by Russ W. Payne.