Arguments For What My Senses Can and Can’t Tell Me About the World and Myself
This section of the sixth and final meditation is for me the most interesting and raises the most philosophical issues. I still remember when I first encountered it 12 years ago in my second philosophy class.
There is nothing that my own nature teaches me more vividly than that I have a body, and that when I feel pain there is something wrong with the body, and that when I am hungry or thirsty the body needs food and drink, on so on. So, I should not doubt there is some truth in this.
The basic argument here is that sensations such as pain demonstrate that humans are a composite of Mind and Body. The fact that we can perceive sensations that belong to Body in our minds is evidence for the Mind-Body hypothesis of humans. We are not Minds that are merely present in a Body “as a sailor is present in a ship”. If this were the case we wouldn’t feel any of the sensations we do. A sailor doesn’t feel pain when his ship bumps into a rock, he only perceives it by sight and understands what has happened via the intellect. Yet we have in intimate awareness of sensations, that are not purely intellectual understandings, when we bump into a pointy object, for example. The same goes for hunger and thirst which are not just intellectual concepts when we feel them.
We are also aware that there are other bodies around us that produce in us sensations of heat, smell, sound, colour, taste, etc… We also know that we have an aversion to some of these sensations, like the smell of rotten eggs; and we have attraction to others, like the taste of pizza.
Of course sometimes what our senses tell us about the world can sometimes be false. In this case I’m not talking about optical illusions and such, but that the way in which information about the world comes in through the senses shapes the way we think the world is structured. Take for example the sensation of heat: Is there actually a thing “heat” which I am perceiving? It’s kind of interesting to think about. In everyday language we still say, “that’s hot” but our scientific understanding of the world contradicts this idea.
This is where Descartes really got it right. On the Aristotelian view, objects that were hot contained an essence, “hotness” (not the kind that some chicks have–another kind) and when we feel heat we are somehow perceiving a thing/essence “hotness”. Descartes on the other hand had a mechanistic view of the world. Although the idea of heat as being average kinetic energy hadn’t been discovered yet Descartes had an idea that was very close. His idea was that the particles that made up a body were rotating very quickly and these particles interacted with nerve endings which sent a signal up the neural pathways to the part of the brain which was the interface with the mind. For Descartes (and any modern person) we know that if I were to perform an autopsy of a hot object, I would never find any thing I could point to and call “heat”. As a general explanation it’s quite amazing how close to being right he was.
So here’s the cool part. Suppose I stub my toe (again) on the “Gotdamned” chair again. According to Descartes the pain I feel does not exist in my toe, but in my mind. Of course it sure doesn’t feel that way but again this is a case where the way our senses function to perceive the world causes us to draw false conclusions about the world. Pain is not a property of Body. Pain (a sensation) is a property of Mind, thus the pain is a consequence of an interaction with Body but the pain itself is not in mah toe. If I cut the nerve route from my toe to my brain/Mind, I would have no sensation of pain. Pain is really our brain/Mind telling us “there is damage to sector 7G”.
In the Aristotelian view the pain actually exists in the toe. It’s really there, just as properties of mass and shape are. As an aside, I think it’s kind of interesting that despite centuries of science we still speak of the world in the Aristotelian sense. I guess you could make an pragmatic argument for speaking of the world in an Aristotelian way. It’d be quite a mouthful if every time you stubbed your toe you said, “Got damn particles in that chair collided with the particles in my toe, which initiated a chain reaction to the part of my brain that is the interface with my mind and produced a sensation that I call ‘pain'”.
The bottom line is that the purpose of sensory perception is not necessarily to tell us how the world actually is but to help us navigate the world by informing us what is beneficial and what is harmful. I think this is a really important philosophical point and one that even everyday people misunderstand (say it ain’t so!). The issue is whether the world exactly resembles the way we perceive it. Within philosophy of perception and epistemology there are some that say that there is no way to know because we can never step outside of what we perceive in the “theater of mind” and there those that says there is a one to one relationship…and as you might expect the bulk of people’s opinion is somewhere in between.
Descartes answer is that our perceptions of Body resemble the modes of Body that are necessary (size, shape, extension, mass); however this is not the case in the other modes of Body. In the case of the non-necessary modes of Body (eg., scent, colour, texture, etc…), there is something (structure perhaps) in the body that produces in us as sensation of a property, but the property we perceive doesn’t resemble the property in the Body that caused it–although it is not ruled out as a logical possibility.
This is a little bit complicated but bear with me: Lets take colour for example. Suppose I’m looking at a purple cup. Is the cup actually purple (an essence) or is there something about the structure of the the cup that produces in me the perception of purple? Does “purpleness” fly from the cup into my eye? Probably not. Descartes gets this right too: We know that the surface atoms of the cup are structured in such a way as to absorb all wavelengths of light except purple; it’s not really purple as in, the atoms are all coloured purple.
So, because of the structure of the cup, light of only 1 wavelength of reaches my eyes. Now, is the light that reaches my eyes actually purple? No, it’s just light waves at a certain frequency. It just so happens that when my eyes receive light at this particular frequency it produces a certain nerve impulse that produces in my Mind the (phenomenal) sensation of purple. Had the light waves been traveling at a different frequency, it would have resulted in slightly different nerve impulses which would have produced in my Mind a different phenomena of colour.
Also, if my brain were structured slightly differently, maybe the wavelength that now produces in me the colour purple might produce in me the colour red. This raises a tangential issue, which is that when it comes to these secondary modes there is no way to know if one person’s experience “purple” isn’t another person’s experience “green”. The things is, it doesn’t matter so long as we all make the same distinctions and call it the same thing.
Now lets try to relate this all back to our starting point, that our senses don’t necessarily tell us about the world as it is but tell us instead how we should best navigate our world. Lets go back to the subject of “pain”. Through faulty reasoning I may come to the conclusion that the “Got Damned chair” I stubbed my toe on has something in it that is “pain” that is now in my toe, or that a fire has something in it that is heat. But fire is not made of any thing called heat any more than my toe is has something in it called pain. Nevertheless, my sensory perception of my interaction with these entities tells me that I should avoid striking the chair with my toe and should not put my hand (or any part of me for that matter) in the flame–unless it is into the feh-laaaaaames of passion.
But If God’s So Good, How Come Sometimes Our Senses Tell Us to Do the Wrong Thing?
Descartes realizes he has a little problem if he is going to simultaneously hold that a) god isn’t a deceiver; b) that he wired us (are there wires in clay?) in such a way were we can be deceived about the world; and c) sometimes it seems that our sense perceptions of the world lead us to the wrong course of action. Descartes explanation is that although there are situations that can arise where our reaction to a stimulus isn’t the best one, the fact is that most of the time it will be. God wired us in the way that will bring about the best response to deal with situations that will most frequently occur.
Here’s an example: Suppose you have a wound on your finger and you need to put some sort of disinfectant on it and this disinfectant stings upon application. The problem is that your sensory system, whenever you put the disinfectant on says “ARUGA! ARUGA! ARUGA! We are sensing pain. Begin evasive maneuvers immediately!” Our sensory system is giving us a message that is actually detrimental to us in this particular circumstance.
Descartes would concede that this is true but that more often than not moving your limb away from things that cause the sensation of pain is a good thing and will preserve your life and health longer. Therefore god’s still a good guy after all. I think this is a pretty good argument and if we substitute “natural selection” for “god” we have a good modern argument. Ta! Da!