The Third Cartesian Error – in One Post!

The main development or change in how Descartes understands the mind from Meditations on First Philosophy to Passions of the Soul is that in this latter book his theory makes it possible for the body to act without the mind. In fact, I argue, he doesn’t leave the mind any way to affect the body at all even though he of course wants it to. There are a couple of reasons for this state of affairs. First, as we saw in the first Cartesian Error, he argues that the only thing the mind can do is think, and the body cannot think at all. Then in the Second Error, he argues that emotions aren’t thinking and explains that the human body works in such a way as to be able to start, continue and end emotions and emotion-based behavior. I call this organization, this explanation, an example of half-duplex communication between body and mind, a type of communication I previously said was exemplified by walkie-talkies and text messages. Let’s briefly review why this can’t be a reasonable way to look at how the mind and body interact.

If the mind were like a walkie-talkie, by definition only one end at a time can communicate. So if you had a spider on your leg, what would have to happen for you to get rid of it? First, the body would feel the pressure on your flesh. But for your mind to know the spider was there too would require one of four things, all of which have problems and raise more questions than they answer, (at least for Descartes):

1) That by a stroke of luck, at the same moment when the body felt the pressure, the mind happened to not be communicating out any messages and so is  able to receive transmission, OR

2) The body not only feels the pressure on the skin, but also “knows” that the mind should stop transmitting and instead listen, and can force the mind to do so by accompanying important messages with a message such as “over” to tell the brain to start talking, OR

3) The body itself would just “know” how to stop the bug (like a reflex), OR

4) The body is constantly transmitting messages whether or not the mind is in a position to hear them, and sometimes it listens in for whatever reason.

On the other hand, Plato, Aristotle and Lucretius argued for something different, an interactive and reciprocal communication between the body and the mind (and the emotions), a process I called duplex communication. For them, the mind and the body are both duplex transmitters, such as cellular phones, which allow two constantly running communications to both be understood by their targets.

This not only fits common sense and firsthand experience, but our more advanced understanding of the body tells us this is correct. Duplex communication between the brain and the rest of the nervous system throughout the body allow for immediate response to outside stimuli by real-time measurement and analysis – Plato, Aristotle and Lucretius each saw that the body feels things that don’t quite rouse the mind, and that our bodies are actually sentient – aware – in a way akin to the way the mind is. The duplex process also allows for conscious analysis of the stimuli, the body’s responses, the results of the responses, what goals are being achieved, and what goals might be better, as well as the ability to seek after those goals. The body can run “on its own” but a conscious person can study her reactions and change her behavior to her preference. After all, they are made of the same stuff. Half duplex communication doesn’t allow this.

So the third Cartesian Error is that the theory cannot explain how the mind and body could have duplex communication, which the P-A-L theory gave an excellent argument for, and which I conclude is a fundamental aspect of the emotions backed up by contemporary research. More specifically, third error has to do with how Descartes thinks the mind and body communicate with each other.


Descartes’ half-duplex theory argues that the mind/soul is united to all parts of the body, not just the pineal gland (If you read carefully this theory is also there in Meditation VI) but that the soul is able to exercise its unique function – thinking – best in the pineal gland (and its my opinion that he really does think of it as more physically extended than he is usually given credit for). He says that the soul and body act on each other by taking turns “radiating”: as in the soul “radiates” into the rest of the body from the pineal gland. Think of it as sort of like an x-ray in reverse. Instead of shooting x-rays through our body to give us an image of our body, things like bears shoot ‘bear-rays’ at our eyes. A similar process happens from the pineal gland to the soul and vice versa. This is completely incorrect but such particulars don’t really matter. What matters is that he has in mind a physical process by which he thinks we receive our sensory information, and it works like in the diagram above. Think of sending a text or SMS message to a friend with your cell phone. Basically, what happens is that a message goes from your phone to an SMS site, and the site attempts to deliver your message to the other phone. If it is ‘delivered’, your friend can read and reply in the same manner.

Here is a “play by play” of his argument:

1) the soul is truly joined to the whole body, no part is excluded,

2) because of the centrality of the [pineal] gland’s location the soul can perform its function in a more particular way there than anywhere else,

3) The central location of the pineal gland allows the soul to “better alter the course of the spirits (chemicals) with the slightest movement”.

4) Similarly, the slightest change in the course of the spirits can greatly change the movements of the pineal gland, affecting the soul greatly.

5) This activity can happen because of the “mediation” of the spirits and the nerves and blood that carry them.

6) Our bodies use “fire” or “heat” to make all possible movements, and it is wrong to think that the soul can impart either to our bodies (A5-A8).

So what we’ve learned here is that because

A) Descartes has a complete, purely physical account of how sense perception and muscular movement are possible,

B) we have all manner of non-conscious motion (eating, breathing, walking aimlessly, etc) and

C) He firmly argues the soul imparts no motion to the body,

then it is fundamentally impossible on his theory for duplex communication to occur between the mind and the body. In fact, it seems impossible for him to seriously, coherently defend any meaningful communication between them. At best what he has is a “half-duplex” system, but that doesn’t match reality and it couldn’t work, as we discussed briefly in the sections on Lucretius.

The next post, the last one to focus on Descartes, will discuss the ethical implications of the three Cartesian Errors.

Whew! The last word on the Second Error!

Last time I finished up by saying that because of his interests and assumptions, Descartes was unable to reach the conclusion he wanted, that emotions are purely mental, and that he looked to be forced into one of two other conclusions: 1) that emotions can exist without mental content, or that emotions can exist without the soul; or 2) that his theory contradicts his assumptions because it's actually lends itself fairly well to defending the idea that emotions must be a type of thought and must have a physiological basis. 

Let's have one last closer look. At the very beginning of his book (A1) he explains emotions are "passive events" that happen to the person/soul, but are specifically referring to the person who they happen to. This fits well with his theory of how perception of things like pictures works. However, he also determined that what emotions are made from and how they are made is completely explainable by mechanistic physiology! To put it super-briefly, though he fixes the "home" of emotions in the soul, it is the body and memory that do nearly all, possibly even all, the work of supplying the mental/belief content necessary to start the physical processes that are emotional actions and reactions. This is actually pretty brilliant, but it was a disaster for his beliefs. So he had to find a way out, a way to show that emotions are perfomances of the mind and could not possibly be performances of the body. 

To flesh it out a little more, lets look at how fear would work (A38): he explains that the movements of the body that "accompany" the emotions do not depend on the soul, all that is required to put a passion in the soul is the proper course of certain chemicals towards the nerves in the heart. From there they can then strike the nerves that make the legs move - and sustain the action - which automatically causes movements in the pineal gland, which causes the soul to "feel and perceive" that we are fleeing from danger. This process can be started by a learned response (as a child you saw a bear eat your dog, now you see a bear and you run), or by "dispositions of the organs" (think reflexes or innate behaviors (flinching when you believe you see a snake, even if its a stick). That is, in a word, bodily volition. 

Descartes goes on to explain (A40) that the emotions mainly incite and dispose the soul to will things for which the passions already are preparing the body. To me, that sounds like a rubber stamp, not an instigator.

Perhaps worse, this sort of explanation leads to a very hard question - in what sense is fear a mental object? How is it cognition, the thing that only the soul/mind can do? Consider - don't animals "fear"? If they do, and they don't have souls/minds, how is that possible? (Descartes would say they don' t have souls and don't fear). But beyond that, we've seen that in some cases the body can start and sustain an emotion, like fear, without any direct influence of the soul. So whatever mental content they have is included in them by means other than the soul!

Remember, on Descartes' view, the body is supposed to have absolutely no part in cognition, yet the first two Cartesian errors have already exposed that instead, he's nearly made the mind/soul impotent or redundant, a position that we'll see later fits easily with Sentimentalism in ethics.

While Descartes is making these points, he also tries to tie on a couple of saving moves: 1) He argues that the pineal gland is really where emotions are felt, even though they feel like they are happening in our body (A33-34), and 2) he argues that the only use of the emotions is to inspire volition/will in the soul (A52). If these two things were right, he'd be making a decent case that the emotions provide the initial motivation for volitions, create them and sustain them. BUT at the same time he is denying #2, saying that the emotions incite a "will for" doing actions they already prepare the body to do, and #1 is very hard to believe (much less prove). 

To conclude, bodily voliton exists: In at least some cases the body is already performing and doing what needs to be done in emotion-situations, as well as in day-to-day actions, just from an image in the brain ("bear") + either learned responses or human nature, and though he wants it to be that the souls is ultimately the "decider", it really seems to be a lot less involved than that. Descartes' theory has two arguments smashing into eachother - one explaining how the emotions are of the body, and the soul is irrelevant, and another concurrently arguing that the body is merely the substratum on which the emotions of the soul perform.