Mock dialogue of the Theist/Atheist discussion here.

[Jenny A]

---

What if you perceive you yourself have an objective value but don't know how to measure it? Why is that impossible rationally?

To give an example, I see the moon. I know it has a mass. I don't know how to measure it but I know it has a weight. 

Why can't the same be true about the perception of myself?

---

The physical effects of the moon are quantifiable.  If we do measure it, we will reach the same conclusions about it's mass. We both know it has mass and that that mass is quantifiable.  If we pretend it doesn't exist, it won't go away.  It will still reflect the sun's light. It will still affect earth'so orbit. In short it exists.

Harry Potter exists in our thoughts.  But we don’t all have the same picture of him, and we can't weigh him. Unlike the moon, if we all cease to think about him, he will cease to exist. God exists in exactly the same way as Harry Potter, no more, no less. That is to say they are both thought constructs nothing more.

That just shows if we have objective value it's not determined by our own or other people's thoughts. So would you agree if we can perceive we have objective value, we ought to ask "how?" when my perception is not that which determines that value nor anyone else for that matter. How does it exist (the objective value of myself)?

Exactly, if objective value exists (and anyone who doesn't believe in objective reality doesn't live long) our perception of it does not change it. How it exists isn't really a useful question unless we have some means of answering it.

But, then you turn to self, beauty, and justice. In a very real sense, these things do not exist. They are attributes of our thoughts not things in the real world. They are products of your brain. When you describe the moon as beautiful you are describing the inner workings of your mind and the culture in which you live's subjective values. But you aren't describing the moon.