Lecture 20

1. Lecture 20 Theories of Consciousness, Consciousness and the Mind-Body Problem

2. Theories of consciousness

3. Dennett’s Multiple Drafts Model • Dennett’s Multiple Drafts Model is the conjunction of several theses. • The Parallel Processing Thesis: All mental states result from parallel processing, i.e., from many simultaneous, interacting sub-processes. • Example: you see red, black and silver, as well as rectangular and circular shapes. Your mind processes all these elements simultaneously, producing a perception of a car.

4. Dennett’s Multiple Drafts Model, cont. • The Multiple Drafts Thesis: At any given time, one’s parallel processing system produces a variety of “drafts”, i.e., of sequences of events that one could become conscious of. • Example: You have a conversation while driving. Your parallel processing system produces two drafts: one consisting of the conversation and the other consisting of the passing scenery.

5. Dennett’s Multiple Drafts Model, cont. • The No Editor-in-Chief-Thesis: There is no mental faculty (“editor-in-chief”) that selects some drafts for consciousness (“publication”) while rejecting others. • The drafts that we seem to be conscious of are typically those that have been “probed”. • Example: You have no memory of the passing scenery, but only of the conversation. This might suggest that the conversation draft was selected for publication and the scenery draft was not. However, if someone were to probe your memory, you would remember bits of the scenery.

6. Dennett’s Multiple Drafts Theory and the Phi Effect (To view the experiment, go into Slide Show mode.) The Phi Phenomenon is when a succession of still images produces a perception of motion. At certain combinations of spacing and timing of the two images, the perceiver will report that a dot moves from left to right and that, half way through its motion, changes color. (In this case, from green to red.)

7. Dennett’s Multiple Drafts Theory and the Phi Effect, cont. • Clearly, the brain uses the information about the green and red dots and mistakenly infers that the red light moved and changed color. • Problem: If the brain uses the information in this way, why do we not see the green light, then the red light, and then the motion and color change?

8. Dennett’s Multiple Drafts Theory and the Phi Effect, cont. • Two Theories of the Phi Effect: • The Stalinesque Theory: The perceptual input is revised and the memory held fixed. We become conscious only after the perceptual input has been revised. • The Orwellian Theory: We initially have conscious experiences of stationary dots. However, our memory of our conscious experiences gets revised so that we only have conscious experience of a moving dot. • The two theories differ over whether consciousness enters the scene before or after the revisions. • According to Dennett, there is no fact of the matter as to which theory is correct; there are no fixed facts of consciousness apart from probing, and no probing could favor one of these theories over the other.

9. Consciousness and the mind-body problem

10. Nagel on Physicalism and Objectivity • Remember: physicalism is the thesis that only the entities studied by the physical sciences, or entities composed of such entities, exist. • The physical sciences are objective in that they abstract away from particularities. • Example: F=ma abstracts away from the color, etc., of the objects it describes. • Nagel’s Contention: We cannot reconcile the paricular, subjective features of experience with physicalism.

11. What It’s Like to Be a Bat • According to Nagel, there is something that it is like to be a particular conscious being. • Example: There is something that it’s like to be a bat. • This “what it’s like” cannot be captured by objective physical laws. • Example: Full understanding of bat physiology will not give us full knowledge of what it’s like to be a bat.

12. Responses to Nagel • Does Nagel just mean that one conscious being cannot have another’s experiences? • If so, then his claim is trivially true, and physicalism can explain its truth.

13. Jackson’s Knowledge Argument • Imagine Mary, who has been raised by perverse scientists in a black and white room and who knows everything about the neurophysiology of perception. • Eventually she leaves the black and white room and sees a bright red sunset. • Jackson argues as follows: • When Mary sees the sunset, she comes to know that it’s like this (pointing at a red object) to see redness. (Premise) • Mary previously did not know that it’s like this to see redness. (Premise) • Mary previously knew all the physical facts about perception. (Premise) • That it’s like this to see redness is a non-physical fact about perception. (From 1-3) • There are non-physical facts, and physicalism is false. (From 4, definition of physicalism)