just to raise a point about all the "begging the question" finger pointing in this thread:
There are many forms of "begging the question" and most of them are harmless. All deductive arguments are "begging the question".
P -> Q
P
---
Q
You are asserting the conclusion in the premisses (by god, that's nearly the very definition of a valid argument!

). One way that people try to solve this problem is to say that you need to assert the conclusion in one premiss instead of more than one (however: P. Therefore P. is logically sound/valid, etc and a perfectly good argument, it just doesn't say much interesting).
Another way to escape the conclusion that all arguments are question-begging is to say that question begging is an ontological matter. This allows the cogito to escape the charge of question-begging.
Also, most if not all definitions of things end up being question-begging, but not necessarily in a vicious way.
I think after you examine the literature and arguments around it you might decide that question-begging is rarely vicious and is about as good a counter to most arguments as "reasoning in a vaccume" is, as you really can't ever take everything in the universe into account for any argument, so there's always a chance that you're leaving something important out.
So, anyway, carry on, but question-begging isn't a very good objection to most arguments.