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Philosophy E156: Philosophy of Mind Fall 2013. Week 13: Dennett on Qualia. Take a few deep breaths and relax your mind. Stare at the blue dot for 30 seconds. Close your eyes and an after-image should appear.

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Take a few deep breaths and relax your mind.

Stare at the blue dot for 30 seconds.

Close your eyes and an after-image should appear.


“At first, the after-image you see is the color orange; the same after-image will then take on the color blue. The color and shape of this test can be changed (red dot in a green square) and will yield the same results.

“The Orange Card test shows that by staring at the blue dot for long enough, upon closing your eyes, an after-image of orange then blue will appear. Even if it disappears for a second, just by thinking that it will re-appear.. it will in fact, re-appear. Try it.”

the so called argument from illusion
The So-Called “Argument from Illusion”
  • The Argument from Illusion:
  • Howard Robinson’s statement of the Phenomenal Principle:
        • “If there sensibly appears … to be something which possesses a particular sensible quality then there is something of which the subject is aware which does possess that quality.”
  • There “sensibly appears … to be something which possesses a particular sensible quality.”
    • Thus, it follows from the principle that “there is something of which the subject is aware which does possess that quality.”
    • But what is the thing the perceiver is aware of which possesses the quality?
    • It is not an orange-ish patch, since the observer in this case has his or her eyes closed. Nor is it any other everyday object.
    • Thus, there exists something else besides everyday objects that the perceiver is aware of.
the argument for sense data
The Argument for Sense Data
  • Thus, there exist (according to the argument from illusion) objects of which the perceiver is aware that are not everyday external objects.
  • These objects of which the perceiver is aware are not brain states or any other aspects of the perceiver’s brain, since the perceiver’s brain is not orange-ish and has no orange-ishness in it.
  • There are only three sorts of objects of which a perceiver could be aware: (1) objects outside the perceiver; (2) biological objects inside the perceiver; and (3) purely mental objects inside the perceiver.
  • Thus (so the argument goes), the objects of which the perceiver is aware are purely mental objects inside the perceiver.
  • Such objects would be purely private and mind-dependent.
  • Call such objects by the conventional term “sense data.”
    • The singular term is “sense datum.”
the basis for the phenomenal principle
The Basis for the Phenomenal Principle
  • Notice that the Phenomenal Principle is crucial to both the arguments, in the form in which I have presented them:
        • “If there sensibly appears … to be something which possesses a particular sensible quality then there is something of which the subject is aware which does possess that quality.”
      • There have been two popular ways to defend the Phenomenal Principle:
      • First, there is direct experience. In a well-known example, H. H. Price cites a direct experience: that although one can doubt whether there is a tomato in from of oneself one cannot doubt, it might seem, that there is a red and round patch there.
      • Second, there is a linguistic argument. When Price affirms his awareness, he says something like, “I am at least aware of a red, round patch.” The language seems clear: that Price has committed himself to the existence of something that is red and round.
explaining the two facts supporting the phenomenal principle
Explaining the Two Facts Supporting the Phenomenal Principle
  • We can explain the fact of direct experience and the linguistic fact of how we talk if we allow ourselves to appeal to mental objects.
  • Direct experience. The mental object would be what we see in our visual field – notice, e.g., that (1) it seems to have an integrity to it (shape, position, etc.) and that (2) we seem to be able to track it in the visual field – and we can explain (1) and (2) by the existence of a mental object that has integrity and is capable of being tracked.
  • How we talk. When one reports one’s awareness to oneself or to others that there sensibly appears to be something possessing a particular sensible quality, one uses a referring expression to refer to what sensibly appears to possess that quality.
    • For example, “There is a orange-all-over after-image in the middle of my visual field. The orange-all-over after-image is floating.” Notice the referring expression “the orange-all-over after-image.”

And we can explain the meaningfulness of what we say by taking ourselves to refer with the expression to a mental object.

what sense data theorists commit themselves to ontologically
What Sense Data Theorists Commit Themselves to Ontologically
  • The sense data theorist commits himself or herself to the existence of things with phenomenal properties.
  • We must be careful with the word “things,” however, since the things to which there is commitment are not just experiences with phenomenal properties or the havings of experiences with phenomenal properties – although, according to one use of “things,” experiences and havings of experience are things.
  • This is why we say that the sense data theorist is committed to mental objects. The word “objects” conveys a sense of boundaries, a sense of trackability, and a sense that the phenomenal properties cover the thing that is inside the boundaries and is trackable.
metaphysical objections to mental objects
Metaphysical Objections to Mental Objects
  • Nonphysicality. Wholly mental objects are nonphysical. But the world is wholly physical, says the objection. Everything in it must be accounted for in terms of this physical character, since the compositionality required for explanation are not otherwise available. That is, how do we explain mental objects in terms of their parts?
  • Persistence and change. What happens when I blink – do the mental objects persist? What about apparent change – are they replaced continuously or not? It seems as if there should be yes-or-no answers, but it is hard to see where they could come from.
  • Determinacy. When you see a speckled hen, you seem to see that it has a determinate number of speckles without seeing how many. If there is a mental object, though, it should have a determinate number, too. But how could it?
more on nonphysicality
More on Nonphysicality
  • The Leibniz Law argument for nonphysicality:
    • The after-image is orange
    • Nothing in my brain is orange
    • Therefore, the after-image is nothing in my brain.
  • And if it is not in my brain, it is not anywhere in the physical world.
  • Therefore, the after-image is nowhere in the physical world.
  • Therefore, the after-image is nonphysical.
  • Compare this similarly constructed argument:
    • The fruit is orange
    • Nothing in my brain is orange
    • Therefore, the fruit is not in my brain.
  • Leibniz’s Law says that identicals are indiscernible (and vice versa). Thus, if X and Y are discernible, then X is not identical to Y.
  • In both are arguments, there is discernibility. Thus, the nonidentity of the after-image and the fruit with anything whatever in the brain.
why the sense data argument should seem to go wrong over nonphysicality
Why the Sense Data Argument Should Seem to Go Wrong over Nonphysicality
  • Why ought there seem to be a problem here?
  • It is not because we have prior intuitions about Leibniz Law arguments that should make us suspicious here.
  • The sense that something is wrong comes from a commitment to physicalism – the view that the world is physical through and through.
  • If you don’t have a prior commitment to physicalism, you are unlikely to be troubled by the sense data argument.
  • The consensus within philosophy that had most philosophers committed to physicalism for the middle part of the 20th Century has in some quarters broken down.
the paraphrase device
The Paraphrase Device
  • We can eliminate an appearance of an existential commitment in a particular statement and undermine any explanation of meaning that relies on the existential commitment by showing that another statement with the same meaning does not have the existential commitment.
    • The second statement is a “paraphrase” of the first, and we use it to “paraphrase away” the appearance of existential commitment.
how the paraphrase device is used in the adverbial approach to sense data
How the Paraphrase Device Is Used in the Adverbial Approach to Sense Data
  • To see how the adverbialist exploits the paraphrase device, consider two statements roughly like the ones I examined a few minutes ago:
    • (3) I am aware of a red sense datum.
    • (4) I have an orange after-image.
  • According to the sense data theory, there are two things referred to in each of these statements: oneself and a sense datum.
  • But the reference to the sense datum can supposedly in each case be paraphrased away, roughly with statements like:
    • (3’) I am sensing red-ly.
    • (4’) I am after-imaging orange-ly.
  • The fact that the paraphrase statements use made-up words would be irrelevant to the adverbialist, since the view would be that we nevertheless know what the paraphrase statements mean.
representationalist analyses to eliminate sense data
Representationalist Analyses to Eliminate Sense Data
  • According to the representationalist, perceptions merely represent that something has a property.
  • So recall the statements that we began with:
    • (3) I am aware of a red sense datum.
    • (4) I have an orange after-image.
  • The representationalist would analyze these statements in this way, to made explicit the absence of existential commitment:
    • (3”) I represent as of a red sense datum.
    • (4”) I perceive as of an orange after-image.
  • Thus, we have no reason, if all cases can be analyzed in this way, to posit sense data or mental objects.
problem roger shepard s rotating mental image experiments
Problem: Roger Shepard’s Rotating Mental Image Experiments
  • Are these different views of the same shape?
what shepard discovered
What Shepard Discovered
  • Answer is yes.
  • How did you come up with the answer?
  • Typical answer: “I rotated one of the images in my mind’s eye, and superimposed it on the other.”
  • Shepard varied the angular rotation distances and measured the time it took subject to respond
  • He found that the response time was proportional to the angular rotation distance
experimental evidence for the cartesian theater
Experimental Evidence for the Cartesian Theater?
  • Dennett asks if Shepard’s experimental results offer evidence for the existence of the Cartesian Theater
  • But we can ask a weaker question:
    • Do they provide evidence for the existence of mental objects?
  • Dennett’s thought experiment to answer the first question perhaps also answers the second
what stephen kosslyn said
What Stephen Kosslyn Said
  • Kosslyn argued that the images are “assembled for internal display” (Dennett’s words) in much the same way that images on a cathode ray tube (CRT), used in a TV or a computer screen, can be created from computer memory
  • Kosslyn’s idea is that once on the “screen,” they can be manipulated by experimental subjects
dennett on locke on secondary qualities
Dennett on Locke on Secondary Qualities
  • Dennett says that John Locke’s account of secondary qualities (colors, aromas, tastes and sounds):
    • “has become part of the standard layperson’s interpretation of science”
    • “has its virtues”
    • “gives hostages: the things produced in the mind”
      • “the idea of red”
secondary qualities
Secondary Qualities
  • Recall that on Locke’s account of colors, tastes, aromas, sounds and tactile feels, they are regarded as “powers” of objects (to cause sensations)

(illustration from

locke s account of primary secondary qualities
Locke’s Account of Primary & Secondary Qualities
  • “Primary qualities of bodies … such as are utterly inseparable from the body …; and such as in all the alterations and changes it suffers, … it constantly keeps…, viz., solidity, extension, figure, motion or rest, and number.”
  • “Secondary qualities of bodies .. are nothing in the objects themselves but power to produce various sensations in us by their primary qualities, i.e. by the bulk, figure, texture, and motion of their insensible parts, as colours, sounds, tastes, &c.”

Locke’s Essay, Book II, Chapter 8, sections 9 & 10

  • Notice that contrary to the illustration, secondary qualities are powers of objects and in that sense not “subjective”
the origin of the apparent ontological difference
The Origin of the Apparent Ontological Difference
  • On the Lockean account, the ideas of primary qualities resemble the primary qualities in objects
  • But the ideas of the secondary qualities in objects do not resemble the secondary qualities – they do not resemble powers or the primary qualities in virtue of which objects have powers to cause sensations
  • We account for the characteristics of material objects, we might say, by separating those characteristics from others we place in the mind
    • But that means, according to this sort of account, that these latter are separate and must be accounted for separately
    • Separateness is source of Dennett’s dissatisfaction
dennett s idea ce p 373
Dennett’s Idea [CE, p. 373]
  • “According to this alternative view, colors are properties ‘out there’ after all.”
  • “In place of Locke’s “ideas of red” we have (in normal human beings) discriminative states that have the content: red.”
  • “We can compare the colors of things in the world by putting them side by side and looking at them, to see what judgment we reach, but we can also compare the colors of things by just recalling or imagining them ‘in our minds.’”