Question for Atheists

[Darkstar]

If the universe is entirely material (which it must be under atheistic thinking), then everything that exists or happens is fundamentally just chemicals reacting.

What exactly is meant by "material" in this context? Energy exists in addition to matter, yet I would be hesitant to label pure energy as 'material'.

Chemicals, however, cannot act reasonably or morally. We can't take one test tube and say that the mixture in it is "more right" than the one in another tube. Natural laws simply dictate their behavior.

Humans and their thoughts and beliefs, as parts of the universe, are merely chemicals as well. Every idea is a natural string of reactions in the brain. The reactions in one mind lead someone to be an atheist while the reactions in another mind lead to a theist. Sort of like different outcomes in two test tubes.

Okay.
[quote='WonderStruck' pid='737148' dateline='1408940045']
On what basis then can we say that one thought or belief is more rational than another?

For starters I would say whichever thought or belief more accurately matches reality could be said to be rational. We can empirically test hypothesis (usually) to determine if they are rational.
[quote='WonderStruck' pid='737148' dateline='1408940045']
Dead chemistry can't be spoken of in terms of reason.

Strictly speaking, this is true. However, life is not dead, therefore it doesn't (appear to) follow the same rules (even though, on the most basic level it does).

We are all parts and products of a giant chemical universe, atheists and theists alike. How can the universe be behaving unreasonably in one place but not in another?

Reasonable is just a word, a label used to describe what sentient minds deem as reasonable. Unlike, say, electrical charge, reasonableness isn't an inherent property of matter and cannot be quantitatively measured.

It just is. Lines of reasoning become totally subjective since we are all slaves to our particular chemistry. But if reason is subjective, we lose any grounds we had of evaluating statements. If my chemistry makes me think you are unreasonable and yours does the opposite in your brain, since no reaction can be said to be rationally superior to another, then there can be no meaningful debate. Ideas are all equally natural. Isn't that kind of a problem?

Empirical testing can be used to validate certain thoughts or beliefs. It can be a bit mind boggling to try to contemplate brain chemistry at its most basic level, but planes fly, cars drive, and internet forums allow me to post on them. We must be doing something right.