The last word about Mary

What happens when Mary leaves her black-and-white room and has a red colour experience for the first time? Here’s the answer, in outline. (I’ll assume for the sake of argument that Mary has developed the neural circuitry required for colour vision.)

  1. Mary’s visual system begins tracking something red, generating a huge set of active, interconnected first-order informational states, which in turn generate a vast range of reactions and reactive dispositions, both psychological and behavioural. Call this complex of first-order informational and reactive states R1.
  2. Mary’s introspective system begins tracking the states in R1, generating a huge set of active, interconnected second-order informational states, which in turn generate a vast range of reactions and reactive dispositions, both psychological and behavioural. Call this complex of higher-order informational and reactive states R2.
  3. Mary has never instantiated R1 and R2 before and there was no practicable way to induce them in her pre-release.
  4. The informational states in R1 and R2 carry a mass of information about the world and about Mary’s current state.
  5. None of this information is about anything essentially private and non-physical (in the structure/dynamics sense). The informational states involved were generated by tracking physical features which could also be tracked by suitable scientific instruments and which were fully described in Mary’s textbooks.
  6. Mary’s total informational situation is novel. She has not previously instantiated this combination of active, interconnected informational states, and there was no practicable way she could have done so pre-release.

That’s it. (5) preserves physicalism, while (6) accounts for the intuition that Mary enters a new knowledge state. Fill in the details with your preferred theories of perception, introspection, and so on.

There’s no more to say ;)

Posted in Tricks of the mind and tagged .


  1. This does not consider acquisition of language or words to mean red etc.Each word is a quale, experienced or imagined.There can be last word about thought experiments because of its viral nature.

  2. The difficulty for me is the idea of one set of brain states presenting (or combining) information to or with another. It does seem arbitrary to assume that her mind has only 2 sets of states (R1 and R2). If – as your theory necessitates – we accept that there is more than 1, then why not R3 which monitors R2, and so ad infinitum? But none of this would necessarily give rise to any subjective ‘feeling’ or experience. We could imagine a fairly simple computer having as many separate data streams/inputs as you like, but we would have no reason to assume it’s conscious. I have the same problem with Dennett’s ‘multiple drafts’

  3. Does the ‚vast range of reactions and reactive dispositions‘ include predictions/expectations about phenomenology? On certain versions of materialism (Jackson-style), this would have to be the case. But why, one might wonder? Seems to because stipulation. And if not, then isn’t it just missing (I guess that’s the point)? Why should I believe that conscious color experience equals complex informational state?

  4. Thanks Keith. I find your explanations clear and precise and always learn a lot from them.

    You do not use the word “representation” although the description of informational states in point 4 may mean that they are representations (eg, from ‘information about”). If they are representations, then what is their content? Or are they meant to be merely causal relations with no content/accuracy conditions?

    On a related point: are reactive dispositions real patterns recognized through one of Dennett’s stances? Or something else?

    • In your second Dilemma podcast interview, you mention in passing the Predictive Processing framework for the Bayesian brain approach to perception and action. I’d certainly welcome another blog post from you at some point expanding on your understanding of this framework and how it relates to the information states and dispositions you mention in the above post on illusionism.

  5. It’s kind of like how my computer has a USB port but I could in theory use it for years without it ever “experiencing” a device connected to it. If I suddenly plug in a device, it probably will work but only after I install some drivers and upgrade some neglected software. I could even call my computer “Mary”.

    Sorry, just kidding. Good article.

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