Tuesday 3/31

Consciousness II: The Knowledge Argument

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Synopsis

Today we considered the first of several arguments which seem to force us to the unhappy conclusion that there is no physicalist accommodation of the phenomenon of phenomenal consciousness. I say "unhappy" because the lack of a physical account of phenomenal consciousness entails we cannot build a mind: We have, after all, only the 'stuff' around us to use in building a mind; yet if these arguments are sound, no amount or combination of physical stuff will allow us to build a mind which enjoys phenomenal consciousness. Given Dretske's Dictum,

You don't understand it if you don't know how to build it.

we are driven to conclude that the mind must escape our understanding.

Thus much hinges on these arguments. No doubt this explains why the problem of phenomenal consciousness has been one of the most discussed problems in recent philosophy. Some of the best minds philosophy has to offer have been absorbed by it, and some physicists and neuroscientists have begun to notice the enormity of the challenge phenomenal consciousness presents.

Part of the appeal of the Knowledge Argument is surely the simplicity of its explanation. Our intuitions about phenomenal consciousness are teased-out and bolstered by two clever thought experiments, the case of Mary and the case of Fred, which provide us something like a graphic-novel approach to philosophy. Putting it that way is not to denigrate but to compliment: One of the reasons Jackson's original article, "Epiphenomenal Qualia", has generated so much discussion is the accessibility and clarity of the problem he describes.

In the forward to "There's Something About Mary: Essays on Phenomenal Consciousness and Frank Jackson's Knowledge Argument" (Peter Ludlow, Yujin Nagasawa, and Daniel Stoljar, eds., Cambridge, Mass: MIT Press, 2004), Jackson offers this brief on his argument:

There are two main parts to the knowledge argument (in the form in which I advanced it; there have been many versions of it): the part that says that complete physical knowledge is not complete knowledge tout court (or anyway not as far as the mind is concerned), and the part that says that if physicalism is true, it is. The final step is then modus tollens. The first part is the part supported by the plausibility of the contention that Mary would learn something about what the world is like on her release. As we might put it, she would acquire an enlarged view of the available dimensions of similarity in our world. Before her release, runs the first part, she knew a lot about how different people looking at ripe tomatoes typically were alike, both in themselves and in their relations to the tomatoes. She knew, for example, how the ripe tomatoes typically induced a tendency to use the word 'red' in such people, provided they were English speakers. After her release, she would realize that there was another dimension altogether to how they are alike, and to how they differ from people looking at, say, grass. The second part of the knowledge argument is the part where it is observed that because she knows all there is to know physically, this means that were physicalism true, there would be no dimensions of similarity instantiated in our world other than those she knows about in the room before her release. Therefore, physicalism is false.

In the same forward, Jackson repudiates the epiphenomenalism he formerly believed the argument demonstrated. Indeed, he is now confident the argument goes wrong somewhere, even if it is not clear where. As he puts it,

Although I no longer agree with the knowledge argument, I do think it has been, and continues to be, a major impetus to many important debates that have cast a great deal of light on some very hard problems in the philosophy of mind. In many ways, I wish I could still accept it.

Let us briefly rehearse the case of Mary. Mary is the object of a sadistic philosophical experiment in which she is raised from birth in a black-and-white room. We might even imagine her being tatooed black and white herself to remove any possibility of her ever seeing color. We're not wholly sadistic. We give her a computer with which to learn things about the world. (You shouldn't have to ask: Of course it has a black-and-white monitor!)

Now let us suppose that the physics of color an the neurobiology of color perception are completed sciences. Thus all the physical facts about color and its effect on our neurophysiology are known. Mary, never having experienced color, uses her computer to become expert in these (completed) sciences. So she knows everything there is to know about the physical facts of color.

Now let's let her out of her black-and-white room. Just for fun, let's put a huge, juicy, ripe red apple on a table outside the door so it will be the first thing she sees on leaving the room. Surely she will learn something new, something she would not know before leaving the room: what it is like to see the color red. She will now know, to frame it as Jackson does above, that those seeing the color red are alike in a way she did not, and could not, have known before leaving the room. Yet she knows all the physical facts, so what she now knows is not a physical fact.

Broadly speaking, two responses to the knowledge argument have emerged corresponding to the two parts of the argument as Jackson described them above:

  1. Deny the proposition that "complete physical knowledge is not complete knowledge" (Jackson's own move, interestingly); or
  2. Deny the proposition that all knowledge is physical knowledge while maintaining that physicalism is nonetheless true.

The philosophical gymnastics involved in either response are complicated and fascinating. Suffice it to say that Jackson is correct: We learn much in coming to grips with the argument.

The current state of affairs is not, however, encouraging: There is no consensus on a final solution to the puzzle Mary presents.

Worse, there are other powerful arguments pressing us in the same direction, arguments which come not from epistemic considerations, but from the philosophy of language and philosophy of science. This is not to say our job is hopeless. Rather, we have to handle the most difficult problem in existence to do it.