Further musings written in 2010 on philosophy of mind – on Frank Jackson’s knowledge argument, or Mary the super-scientist.
The Thought Experiment
Mary is a great scientist of vision, but is born without the ability to see the colour red. She gets to learn everything about the physics and physiology of seeing red, and understands everything physical about the process of seeing red including all the associated brain states. Eventually doctors manage to operate upon her and restore her ability to see the colour red. Does she not acquire a new fact upon experiencing the colour red? If something is added, then she must have acquired new facts, something beyond the physical.
- You know all the physical facts about the brain and construct a model
- This model of the brain acts less than the mind
- The mind is more than the brain
The Physicalist response
The problem with this thought experiment is it juxtaposes the very accessible intuition of our everyday experience of seeing the colour red with the totally humanly unimaginable experience of knowing all the physical facts about the brain.
The subjective experience of seeing the colour red is part of our stream of consciousness, and so must arise from a fairly high order process in the brain (or mind!). To know all the physical facts involved in experiencing seeing the colour red, therefore, Mary must have complete atom-by-atom physical knowledge of a large part (most?) of the brain.
One physicalist response is that Mary in fact gains no knowledge upon the restoration of her sight: rather, the complete physical knowledge was enough to already give her the subjective experience of seeing red.
Brains within brains
This may seem absurd. But maybe this is only because we are extrapolating wildly from our normal experience. Learning about visible light or how the eye works clearly gives me no sensation of colour. So however much Mary learns, she will never see a colour (Red, to her).
But what if Mary learned everything physical? She would have to have in her head all the physical facts, to be sure she had not left any out (then she wouldn’t be able to claim to have gained new, non-physical ones). Every atom, all the laws of physics that dictate how they behave, all the biological knowledge of how the brain works. She would have an entire working model of the brain in her head.
She would have an entire working model of the brain in her head.
First, how can Mary store an entire working model of a brain as complicated as hers in her own brain? Perhaps this is where some of the dualism slips in?
Second, putting this aside, it is clear the thought experiment goes way beyond any point where our intuition will be accurate: we can never imagine modelling a complete other brain inside our brain in real time. Instead, we have to imagine Mary as running this virtual brain inside her own, and stimulating with “red” input.
If the brain is only physical, then Mary now has all the apparatus – including the correct input (in terms of the correct frequency of light which she inputs into her working model of the brain) to see red – and it’s running in her own head. Since she now has a second working (if virtual) brain inside her own head – and this brain will experience redness as conscious qualia – isn’t Mary now experiencing redness herself?
Intuition pump
The thought experiment becomes absurd at the point we try to imagine reconstructing all the physical facts within our own head. We are essentially making a second physical universe within our heads, comparing it to our normal experience, and then saying it lacks something – even though really, we will never know what such a condition is like, any more than we know what it’s like to be a bat.
I think this sort of boils down to the zombie arguments – though perhaps those are a little more persuasive.