> Um, obviously? What distinguishes a person from a braindead patient is that one of the two has a mind. Are you saying that the fact that you talk to a person and have them recall facts is not enough to say that they have a mind? Also, to say that a mind has never been observed either dependent or independent of a brain would mean that the idea of mind has no basis in reality at all.
You're observing communication, which like the gravity example, is one effect that's discernible and understandable to us. Much like the effects of gravity could be observed by people of the past but without sufficient measurements and tools, they did not attribute the orbit of the planets and what glues us to the earth as the same principle.
> The upside of this is that if there's a phenomenon that does not interact with matter in any way whatsover, even indirectly, then that phenomenon cannot possibly have any relevance to human life.
First, whether it has relevance to human life had nothing to do with something being true or not. Secondly, clearly mind does interact with matter, it does so through the brain. We can already construct devices that interact with mind, by making babies.
But we cannot construct devices that can peer into your mind and perceive experience in the way that you do. You might theorize that we should or that science will, someday, but this is a promise not unlike religious ones.
> What aspect of reality informs that belief of yours?
The most fundamental aspect of reality is that which perceives reality in the first place, aka. your experience. Without this awareness, there is no perception, no memory, no intellect. Without these, there is nothing to construct and hold the theory of how mind came to be out of matter.
Fundamentally, I can posit that it is all a dream, the matrix, plato's cave, etc, but whether the contents of experience are illusory or not, it can't be denied that there is the fact of experiencing taking place.
The scientific fundamentals are posited on the premise of "if we didn't exist, what would we agree on is true about the universe". And that's a valid endeavor, but it rests on a hypothetical because we do exist as sentient beings.