Jackson

aim

• To argue that there are non-physical facts about conscious experience.

• He uses this to defend epiphenomenalism about qualia: qualia are non-physical and do not cause physical events, even though physical events cause them.

quick key terms

• Qualia: The subjective, “what-it-is-like” aspects of experience.

  • e.g. what it feels like to see red, taste coffee, feel pain.

• Physicalism: The view that all facts are physical facts, or supervene on physical facts.

• Epiphenomenalism: Mental properties (like qualia) are caused by physical events in the brain, but do not themselves cause any physical events.

• Knowledge argument: An argument claiming that complete physical knowledge about the world does not give you knowledge of all the facts (specifically, facts about experience).

fred thought experiment

• Fred has better colour discrimination than normal humans.

• Where we see just “red,” Fred can distinguish two different shades, call them red₁ and red₂, as easily as we distinguish red from green.

• Scientists test Fred and confirm this behaviourally:

  • He can sort red₁ and red₂ consistently.

  • No one else can.

• They look for physical differences in his brain, eyes, etc.

fred shows…

• knowing all the physical facts (say, about his visual system) doesn’t tell us:

  • what his colour experiences are like from the inside.

• This suggests:

  • There are facts about qualia (what it’s like) that are not captured by physical information.

mary thought experiment

• Mary is:

  • A brilliant scientist who knows everything physical there is to know about colour vision:

    • optics, wavelengths, neurophysiology, etc.

  • But she has been raised in a black-and-white environment:

    • B/W room, B/W screens, B/W textbooks.

    • She has never seen colour (like red, blue, etc.).

• She knows every physical fact about colour and human colour vision.

• Does Mary learn something new when she first actually sees red?

  • Jackson says: Yes, she learns what it is like to see red.

new facts?

• She gains access to genuinely new facts:

  • Facts about the qualitative character of experience.

• These are non-physical facts:

  • They cannot be deduced from or fully identified with physical information.

refuting “new facts”

mary only gains:

• A new ability (e.g., the ability to recognize or imagine red).

• Or a new mode of presentation of the same old physical facts.

Jackson’s point: those alternatives downplay the intuitive force that she really learns something about the world and her mind.

jackson argues qualia correspond to non physical facts. new question:

if qualia are non-physical, do they have causal powers?

• He argues that qualia are epiphenomenal:

  • Physical events in the brain produce qualia.

  • But qualia do not in turn cause anything physical

objection: our reports about qualia show they cause things

Example worry:

• When I say “I am in pain,” it seems like my experience of pain causes my verbal report.

• If qualia have no causal power, how do we explain:

  • People talking about qualia,

  • Introspective reports,

  • Our awareness that we are conscious?

Jackson’s reply:

• All those behaviours and reports can be explained physically:

  • Brain states cause:

    • Both the physical behaviour (saying “I am in pain”) and

    • The qualitative experience (pain qualia).

• The causal work is done by the brain state.

• The qualia are produced alongside, but do not themselves cause the output.

objection: evolutionary argument

Worry:

• If qualia were causally inert, why would they evolve?

• Natural selection selects causally effective traits.

• So it’s weird to think that such an important feature (consciousness) has no causal role.

Jackson’s reply

• Evolution selects for physical structures and functions.

• Qualia might simply be a by-product of brains that are good at representing and processing information.

• Natural selection doesn’t need to “select for qualia” specifically; it selects for the physical traits that also produce qualia.

So the fact that qualia exist doesn’t show they have independent causal power.