Mind-Body Problem

The Easy and the Hard Mind-Body Problem

David Chalmers – one of the philosophers participating in the interdisciplinary field of “cognitive science” - argues that one aspect of the mind-body problem is “easy” and the other “hard.” (Chalmers, 1995). In this way, he divides the issue into two separate problems.

The easy problem is the one that mots neuroscientists are concerned with, and it is the one discussed by crick in his Scientific Search for the Soul. Crick attempts to solve the problem by neuroscientific means. His research strategy is to try to find the specific neural processes that are the correlates of our conscious awareness (he calls them the “neural correlates of consciousness,” or NCC for short). Finding the neural correlates of consciousness is a problem of the same general type as finding the neural correlates of anything – language or memory, for instance. Neuroscience has made great progress in solving such problems in the past. Finding the brain regions and processes that correlate with consciousness is simply a matter of directing an existing research strategy from areas of previous success (language, memory) onto a different aspect of mental functioning (consciousness).

We should not underestimate the difficulty of finding the neural correlates of consciousness, but Crick is only looking for which brain regions or processes correlate with consciousness and describing where they reside. He does not attempt to explain how that particular pattern of physiological events makes us conscious. This is the hard problem. The hard problem is a conundrum of a different magnitude – it raises the question of how consciousness (“you, your joys and your sorrow, your memories and your ambitions...”) actually emerges from matter. Modern neuroscience is well equipped to solve the easy problem, but it is less clear whether it is capable of solving the hard problem. Science has few precedents for solving a problem philosophers have deemed insoluble in principle.

A “thought experiment” is an imaginary experiment; the experiment is not really conducted. Photo by Elena. 

John Searle, another contemporary philosopher with a great interest in this problem, suggests the following thought experiment. Pinch yourself (hard) on your left hand. What happens? You feel pain, of course – it is sore. This is an expression of the mind-body problem : something physical happened to your hand, and yet you felt a pain in your mind. Let us see, in terms of the easy problem, how we fare in explaining this phenomenon.

We know exactly what the pain receptors embedded in your skin look like, and how they work. When pressure is applied yo these receptors, a very specific physical process excites the neurons connected with them. This sends a message down these neurons (causes them to fire), which in turn causes a chemical to cross the synaptic spaces at the ends of the axons – using the chemical-dependent neurotransmitter systems. The axons in question travel through a nerve coursing up the arm into the spinal cord and the brainstem, these axons terminate on a second set of neurons in the thalamus. From there the physiological message is relayed again, to a specific part of the primary sensory cortex of the right hemisphere. The pain receptors in the left hand are represented in a specific region of the somatosensory cortex in the parietal lobe, and that is where the nerve fibers we have been tracing terminate. (Pain receptors from other parts of the body map to different regions in the somatosensory cortex, as suggested by the dashed lines). Excitation of the cortical cells in this area causes you to feel pain. This solves (this particular instance of) the easy problem – these are the physiological processes that cause you to feel pain in your hand.

But it is not difficult to see that the hard problem remains entirely unsolved. What turned the physiology, anatomy, and chemistry just described into a feeling of pain? How did that happen?  We have just outlined a purely physiological process (and traced the anatomical pathways it traversed); we have not explained how the process started as something physical but somehow ended up as something mental. Searle used a memorable phrase to describe the hard problem we are left with: “How does the brain get over the hump from electrochemistry to feeling?”

This sort of question was traditionally considered to be a philosophical problem, but it is now being treated as a scientific one – one that might be addressed experimentally.

The Brain and the Inner World, Introduction to Basic Concepts. Mark Solms, Oliver Turnbull.

Do the trees have their own brains? Photo by Elena.