john locke replied 15 years ago (Nov 5th 2008, 12:27:05 am) There seem to be three problems with the theory that all phenomenal events occur literally in the brain.
1. There is no evidence for this claim. All the evidence from neuroscience relates to the neural correlates of consciousness (NCCs). All the evidence from introspective studies refer to phenomenal events. The real problem is not the nature of the NCCs, nor the nature of the phenomenal events, but what is the relationship between NCCs and phenomenal events. As Ayer (1950) showed many years ago, information about how the brain works is not information relevant to the entirely different question of how these brain events are related to our conscious experiences. He pointed out that, if we claim that two sets of events A and B are identical, it is no use piling up a heap of facts about A, or about B: it is essential to demonstrate that A and B are (or are not) in fact identical. Since neurophysiology and neuroimaging only pile up facts about the brain, and introspectionist psychology only piles up facts about phenomenal consciousness, we need something more. In all brain imaging experiments we gain facts about the neural correlates of phenomenal consciousness (NCCs), not about phenomenal consciousness itself. As Ayer (1950) succinctly put it—if we are trying to build a bridge across a river it is not enough merely to raise one of its banks. We need a powerful theory that connects the two.
2. This account does not distinguish properly between phenomenology and knowledge in relation to consciousness. As Edmond Wright has repeatedly emphasized, sensations are phenomenal, but not epistemic, intermediates in perception. In associative agnosia the patient has intact phenomenology but defective epistemology about visual objects. In blindsight the opposite occurs—no phenomenology but functioning epistemology. Visual phenomenology and visual epistemology are processed by different brain mechanisms.
3. The theory contravenes Leibniz's Law of the Identity of Indiscernibles. This states that for two entities to be identical they must share the same properties. Neurons (and their activities) have one set of properties (e.g. size, shape, colour, electrical, etc.) and phenomenal objects (events) have quite different properties within these categories. So they cannot be identical. This is akin to Putnam's claim that "Water is identical to H20", which can be shown to be false by the following argument. If water is identical to H20, then so are steam and ice identical to H20. As 'identity' is a transitive relation, this entails that water, steam and ice are identical, which is clearly contrary to fact.