How do you describe the way the rainbow looks so that a bat could understand?
And, for that matter, how do you describe the way echolocation feels in a way that a human could understand? Whatever the answers to these questions may be, we know what they won’t be:
This is not to say that science hasn’t done amazing things. I think we all can agree that it has. And neuroscience certainly can tell us a lot about what brain-states correlate with particular thoughts and feelings. And there is an almost limitless number of things that can be done with that.
But, what it can’t do is describe those thoughts and feelings themselves.
At least, it can’t do this while remaining science. Such feelings cannot be mathematically modeled and, therefore, cannot be addressed by the tools of science. The first person perspective is simply not a scientific topic.
The significance of this is not that it is the only such thing. Rather, it is simply one of the very few non-scientific entities that the materialist is loathe to deny. In nearly all other cases (spirituality, morality, metaphysics, etc.) the suggestion that our basic human experience contradicts materialism is met with an almost immediate rejection of that experience.
I’ve heard it said that we should adjust our theory to fit the evidence, not the other way around. But I don’t see this occurring in the case of materialism. Anything which can’t be described by it is thrown out as illusory, the same way a flat-earth advocate might throw out photographs of the planet as optical illusions.
Even then, the first person perspective (what it feels like to see a rainbow or echolocate) is simply too hard to deny. But agreeing that there is more going on in the mind than the strictly physical is to abandon the core doctrine of materialism.
But the only real alternative to rejecting materialism is denying that one’s first person perspective exists, a claim so basic that, as Descartes and others have pointed out, it can’t even be denied without assuming that it is true.
This is what runs through my mind when people ask me why materialism needs any defense at all (well, that and the fact that such people would never accept that question as an argument for any other position).
Personally, I think there is reason to reject the maxim that “extraordinary claims require extraordinary evidence”, but it strikes me as odd that many who have quoted it at me also claim a position that requires something as extraordinary as denying that one’s own thoughts exist, while asking (in all seriousness) why they need to offer any reason at all to believe it.