Down the rabbit hole we go...

"...when a physiologist looks at another man's brain, what he sees is in his own brain and not in the other man's brain. I have not so far found any philosopher who knew what I meant by this statement."

-- Reply to criticism of Mr Nagel on Russell's PHILOSOPHY OF SCIENCE

This is one of those few quotes that has stuck with me for years and years and has made a huge impact on my thinking about reality, metaphysics, empirical science, and our understanding of the world around us. When I first read the essay in which the quote appeared, I was almost ecstatic with the implications it had on the causal theory of perception. My brain was literally on overdrive while pondering the significance of Russell's statement and what it meant in terms of how we think of perception, the brain, physics, neurophysiology, facts, the universe, etc. Basically, I reasoned that if we take as a premise that the causal theory of perception is true (one that is based on modern science and observation), then that same causal theory of perception must be false, and more than this, meaningless. But the vicious cycle of the paradox still haunts me. The problem is that most people belief that what they perceive and observe via their senses is real, that is that they can perceive actual physical objects (naive realism). But the problem is that what we observe tells us that what we are observing is not real. And if what we observe is not real, then our reasoning that what we observe is not real is flawed, because it is in turn based on observations that would not be real. I know, it seems complicated and like talking in circles.

Let me break the paradox down into pieces. First, the causal theory of perception basically suggests that when you perceive or observe something, your computer screen for instance, that you are not really observing a physical object in objective space; rather you are only experiencing a mental state, inside of your brain, which is "caused" by the actual physical object, or in this case the real computer screen as a physical object. Let's break it down even further and analyze what it means to "see" by basic scientific processes. Physics tell us that light strikes physical objects (or bundles of energy, however you want to put it), and those objects absorb some parts of the light spectrum and reflect others. What is reflected is what we construe as the "color" of the object, though color is really not even a real characteristic of the object, according to physics, because the object does not posses that color, rather it only reflects it. Next, physics tells us that those reflected spectrums of light propagate through real space, and ultimately strike your eye balls. Now the physiologist takes over, who says that when those spectrums of light (now photons...here arises the wave/particle paradox of light) strike your eye balls and ultimately your retina, that initiates a neurological impulse through the optic nerve. That impulse makes it way to the brain and is processed accordingly. Next, the cognitive psychologist tells us that our brain sorts, filters, and compares this data and ultimately gives us a perception that we refer to as the "computer screen". This is of course an over simplificaiton, as I am not a physicist, neurophysiologist, or cognitive psychologists, but hopefully you get the gist of the process. It is basically a causal chain of events, where we as "observers" only experience that last link of the chain of events. So, if we are experiencing the link on one end of the chain, and a physical object is represented by a link on the other end of the chain, then we really have not access to that physical object.

Now, just read the above paragraph a few times and really think about what this means. Sleep on it. Have a few drinks and ponder it again. It means that what you are seeing as you read this text is not "really" the physical computer screen; rather what you are perceiving is all in your brain, or in your mind, etc. And what this means is that you are really entirely divorced and isolated from the real world of physical objects. It means that "you", in the strict sense of the term, and your perceptions are completely encased inside your skull and inside your brain. You are truly alone and isolated from any so-called real world, including your own body and anything that you think you can perceive via your five sense....it's all just a series of mental states caused by your brain. It is as if you were a tiny person sitting inside your brain, and your eyes are video cameras that pipe data from the outside world into your brain and project it for your your mind's eye. But the frightening thing is that you have no clue whether what you are perceiving possesses even a remote resemblance to the real thing. In fact, as I'll suggest shortly you don't even know whether there is a "real thing". I know it sounds absurd, but this is what the observations imply. We can trace this very clearly, via observation, from light and objects, to our eye, the retina, and to the brain.

Maybe now you have caught on to the paradox. Maybe you are thinking to yourself, wait a minute...if our observations tell is that what we observe is not really real, but only inside our brains, doesn't that mean that those same observations that tell us that what we observe is not real, are themselves not real? Yes, precisely! Our observations and reasoning therefore negate themselves. That is the thrust of the paradox, and that is exactly what is implied by Russell's quote above. What the physiologist sees when he is peering inside another person's brain, is not really that person's brain, but inside his own brain. And if you had a second physiologist in the room, and he was peering inside the brain of the physiologist peering inside the other person's brain, you could say the same thing of his, an ad infinitum. And if that is true, then he really can't use those observations as evidence to suggest that what he is observing is just in his own brain. In other words, Russell's quote negates itself and with a paradox.

Where do we go from here? Well, there are a lot of options, and I won't go into them in detail. One option is that we assume that the causal theory of perception is true, but that what we observe basically a facsimile of the real thing. Using the video camera analogy, this would mean that what the camera records and plays back is visually not that different than what we would see in place of the camera. This is very strange, but it basically requires reasoning by analogy. Analogy is not very reliable form of reasoning, by the way. Cameras do this for us. So do our radios and stereos, which somehow reproduce sounds that are very close to their sources. So why not in the case of the sensor organs and brain? Perhaps.

Another option is that there really isn't an "outside", and that what we perceive is really all there is, and that there is nothing "causing" our perceptions. I am inclined to follow this line of reasoning, yet it really means that you have to be careful in what you attempt to deduce from your observations. It means that when the physiologist is observing another person's brain, he is not observing a physical object or just a mental state that is caused by a physical object; rather, he is just aware of "something", something neutral, where we really can't speculate whether is caused by anything or not. He can't really take his observations and use them to infer that something exists outside of his observations, because for all practical purposes, his observations are all there is. This option has its absurdities as well, of course, but it does prevent us from using our observations to negate themselves via a paradox. This option also suggests, to no surprise, that much of our theories about the world, are really just models or metaphors that allow us to manipulate and re-interpret our raw observations.

Kris Hartung