@hecks - "You keep saying that, because I don't share some immutable foundational truth with another secular humanist, my beliefs can't be rational."
I am not saying this. In fact, after this conversation, I'm quite positive that your beliefs *are* rational. They are rational in the sense that they all cohere together to form a system which makes logical sense and can plausibly account for the things that need accounting for in our universe. And I think, based on other things that you have said, that you would agree that my beliefs are also rational in that way; that they cohere to form a plausible explanatory system.
The relevant difference, I think, is not the rationality of our systems but the rationality of our starting points. That is, if I grant your starting point then your system, because it is rational, is right. I take that if you were to grant my starting point that the Scriptures are authoritative in all they teach, then you would think that my system, being rational, is right. The issue is how we epistemologically justify our starting point and, from what I understand, the only way that you can justify yours is by nothing that your observations of the world are unique to you and no one else, and thus that the rational system you construct from those observations is right, but only for you. This is what I take you to be saying. If I am wrong, please correct me.
My point, when I said that people generally observe the same things, is that every individual human being has a problem, regardless of where they live, how wealthy they are, etc. The problem is their own existence. For human beings, our existence is a problem to us, something we must solve, something that needs explaining. Each person observes their existence and wonders at us and feels a need to explain it. In that very general sense, our observations are the same. I grant you that many other things are quite different, but this particular problem is proper to all humans.
So, this one observation, that we exist, is the same for all of us. And, as I said, reason and logic are really just methodologies to help us get to where we have to go. If logic and reason were able to guide us, then, based on our shared observation of our existence, we would all come to the same conclusion about it. But we do not. Which means that people *interpret* their existence differently, and that this interpretation is *logically prior* to the application of reason and logic to the problem. Whatever this interpretation is, it does not seem to have the status of a rational basis for establishing belief in a conclusion, because it is just an assumption, probably a culturally socialized assumption, but still an assumption.
Christianity, it seems, gives good reasons for the assumptions it makes about our interpretation of our existence. At the very least, it gives reasons. Humanists don't seem to give reasons for their particular starting points when it comes to the problem of human existence. They assume them, and then use logic and rationality as red herrings to give the appearance that their systems are unassailable. Given the starting point, they are, but my point is that there is no reason to assume that any particular humanist's starting point is better than any other.