Why do Athiests require 'proof' that God exists?

[genkaus]

Points 1 &3: Agreed. What I hoped to address was the dismissal of any ‘proof’ other that physically observed phenomena or empirically supported inferences. That shows an unwillingness investigate the intellectual tools and methods, like the scientific method, we use to investigate the natural world. Materialism doesn’t get a free pass on its metaphysical assumptions.

So far so good.

Point 2: Sure. Angels, symbols, and qualia fall into different categories of being. I don’t see that as directly relevant to the discussion, which I’m trying to focus on subjective experience.

This point addressed your statement that "the demand for physical proof of metaphysical entities is not a valid request". Clearly, since not all entities are equivalent, we cannot blanketly exempt them from physical proof.

Point 4 (the important one): Materialism does not adequately address the issue of subjective experience because it only speaks to half of the problem: brain functions. Materialist explanations of consciousness focus exclusively on operations, i.e. observed behaviors, neural activity, etc. The missing part is why the brain feels the way it does, i.e. how this specific form of wet grey matter gives interior life to our thoughts and sensations. ‘Emergent properties’ are sufficient for describing how various functional components can join to perform new functions, like gears and levers assembled into spring driven toys. Going beyond that causes a category error because combining simple physical operations to make a single complex operation is much different than making a sensation, or qualia.

I'd disagree. We've already seen such category shifts occur at higher level designs. For example, one might say that there is not reason why component chemicals coming together should give rise to the completely new phenomenon of life - which includes self-initiated motion and reproduction. Or how putting together various batteries, semiconductors and microchips together should not give rise to software. The emergent properties here - both life and software - are qualitatively different from and aren't found in any of the component pieces. Why wouldn't the same concepts be applicable to sensations, feelings or emotions?

First I would like to know, from a materialist perspective, why one set of neurons firing, identical to all others except physical location, gives rise to pain, another to the smell of vinegar and another the memory of your grandmother.

You are wrong if you think that they are identical in all aspects other that physical locations. The pathway or the series in which these are fired are different. Their arrangement and amount are different. There may be many more differences that we don't know about yet. For example, there may be three separate arrangements of units for pain, smell and memory and these units further arranged in a more complex manner to form the perception and memory centers.

Next, is sensation limited to biological matter and why? For example, if a robot behaved like a human does that automatically make it a sentient being?

Firstly, I don't think sensation is necessary for sentience. Even without the uniquely human capacities of seeing and feeling, perception is still possible and a machine capable of perception and reaction would likely be sentient as well.

Once we do understand the structure of our neural network, we may be able to mimic its properties electronically. Once that is accomplished, I believe the machines would be able to "feel" or experience sensations as well. Though, unlike god, I think only an exceptionally cruel scientist would give them nociception.