Chalmers: Psychological vs. Phenomenal Properties
Consider pain. Pain has a particular functional role: it is caused by events which have a tendency to harm the organism; it tends to make the organism dislike whatever caused it; and it leads to behaviors such as avoidance. (These are relations to inputs, other internal states, and outputs, respectively.)
Pain also has a distinctive phenomenal character: there is a particular way a pain feels (though this may be different from one kind of pain to another).
It's not really clear which of these is more important to the analysis of pain. You might be able to make a case for either as the fundamental aspect of pain. But at least it's clear that both these things are closely associated with pain.
Chalmers calls the first, the functional role, the psychological aspect of pain, and the second, the way it feels to be in pain, the phenomenal aspect.
Many mental phenomena seem to have something like this double aspect (while others seem to have mainly one or the other of the two aspects). Examples (references to Chalmers are to The Conscious Mind, Oxford University Press, 1996):
| psychological aspect (very rough & ready account) | phenomenal aspect | |
| pain | caused by potentially harmful stimuli; tends to make one dislike the cause; leads to avoidance behavior | what it feels like to be in pain |
| learning | cognitive capacities adapt to new circumstances and stimuli (Chalmers, 18) | none? |
| perception | "cognitive systems are sensitive to environmental stimulation in such a way that the resulting states polay a certain role in directing cognitive processes" (Chalmers, 18) | experience of perceiving something |
| sensation | none? | a certain felt quality of experience (consider having a reddish after-image, or an itchy sensation) |
| belief that P | typically caused by the fact that P; leads to behavior which will tend to allow one to satisfy one's goals if P is true; allows the fact that P to influence reasoning processes (cf Chalmers 19) |
Consciousness and Awareness
Still following Chalmers' discussion: we associate consciousness with a variety of primarily psychological aspects, including: awakeness (not being asleep), reportability (ability to answer questions about my own mental states), attention (consciousness of X seems to be a matter of attending to X), etc. (Chalmers, 26-27). These are all primarily functional notions.
Chalmers suggests that there is a psychological property associated with experience (i.e. with phenomenal consciousness or qualia). He uses the term awareness for this.
"Awareness can be broadly analyzed as a state wherein we have access to some information, and can use that information in the control of behavior. . . . Awareness of information generally brings with it the ability to knowingly direct behavior depending on that information" (Chalmers, 28).
So we have a distinction between phenomenal consciousness (which Chalmers usually just calls "consciousness") and awareness. Other people have used other terms for pretty much the same distinction -- for instance, Ned Block distinguishes "P-consciousness" (phenomenal consciousness) from "A-consciousness" (short for "access consciousness," and more or less synonymous with Chalmers' "awareness").
The "Easy Problem" and the "Hard Problem" of Consciousness
The "easy problem" is to give a physicalistic account of awareness. Awareness is a "psychological," i.e. functional concept. We can explain it physicalistically by accurately defining its functional role (a philosophical project?) and then explaining what physical process plays that role and how (a task for psychology and neuroscience). We may not have carried out either of these tasks yet, but at least we know how to proceed, and how to recognize success once we achieve it.
The "hard problem" is to give a physicalistic account of phenomenal consciousness. What makes it hard is that it's not even clear how to begin. Phenomenal consciousness doesn't seem to have a functional characterization. (As soon as we try to characterize it functionally, we end up with a "psychological" notion which it seems in principle possible that we could have without having any qualia.)
The Explanatory Gap
The explanatory gap is one way of putting what makes the hard problem hard. There seems to be a gap between physical explanations and phenomenal properties. This does not just mean that we haven't provided a complete explanation yet (although that's part of it). We don't have a complete explanation of awareness either, but at least we know how to go about getting one. The "explanatory gap" refers to the problem that in the case of qualia it's just not clear how there even could be a physicalistic explanation.
To turn this observation into an argument against physicalism, we need something like this:
1. There is an explanatory gap between physical and phenomenal truths. (That is, no amount of knowledge about physical facts seems to give us an explanation of phenomenal facts.)
2. If there is an explanatory gap between physical and phenomenal truths, then there is an ontological gap between the two. (That is, if knowing about the physical facts doesn't allow us to know about the phenomenal truths, then they must be about different things.)
Therefore,
3. Materialism is false.
Arguments against Supervenience
Let's focus on the inverted qualia argument. (The zombie, or absent qualia, argument is similar.)
Sometimes the inverted qualia argument is simply taken to be an argument against functionalism, not against physicalism in general. In that form, the argument is:
0. If functionalism is true (of qualia), then it is a necessary truth that someone has the qualia they have if and only if they are in a certain functional state. (This must be a necessary, not contingent, truth, because functionalism purports to be an account of the essential nature of mental states.)
1. It is conceivable that there could be two people who were functionally identical, but who had different qualia. (The qualia of one are inverted with respect to the qualia of the other.)
2. If something is conceivable, then it is possible.
Therefore,
3. It is possible that there could be functionally identical people with different qualia. (from 1, 2)
Therefore,
4. Materialism is false. (Since 3 is incompatible with 0.)
Possible real example: "pseudonormal vision."
Some have tried to generalize the zombie and inverted qualia arguments into arguments against physicalism in general: we can imagine all the physical facts being the same, and yet qualia being different; if imaginable, then possible; etc.