OK, what IS the right classification...

[Cinjin]

...for this fallacious line of reasoning:

Step 1: Assertion is made without supporting evidence
Alt Step 1: Definition is invented to suit step 2.

Step 2: The unproven assertion and/or contrived definition is used to prove something else.

We see this line of reasoning used a lot in some of the more popular philoso-babble arguments for Christianity.

"Moral goodness is grounded in the very nature of Yahweh. That's why everything Yahweh wills or does is good."

"Without Yahweh, there can be no absolute morality and since absolute morality exists, God exists, and this god is of course Yahweh, who else?"

I've been calling this "begging the question" but I realize that's not quite right. Or maybe it is? Please set me straight on this point.

Regardless of what you want to name it, it's still the credulous man's argument - cyclical in nature and "evidenced" by faith.

Every argument regarding creation, sin, mankind, morality, etc will always comes back to one thing: Do you believe in God? Asking a christian to provide evidence for anything in the natural world without the cyclical argument is absolutely pointless. It is the primary support of their belief system. Which is why we keep hearing the same arguments decade after decade. While science and research continually offer the enlightened new ideas and concepts month after month, they are stuck in the dark ages with their one holy "irrefutable" argument.

I don't know that I'd call it begging the question, but I can see where you're coming from.