I got a request to look at an analogy originally presented by Matt Dillahunty, so I explain why it’s a bad analogy. (Oddly, some atheists don’t seem to understand that to call something trivial is to say that it’s true. They seem stuck on the idea I’ve missed the point that reserving judgment is not identical with affirming a negative; which is true but only important in cases where one doesn’t have to act on the truth or falsity of the proposition, which has nothing whatever to do with whether God exists.) There’s a correction or two I should note, such as the original example was gumballs instead of marbles, and in some examples he specifies whole gumballs.
(I’m coming out with a scripted version of this video which will be much tighter, by the way.)
You can of course watch it on YouTube, too:
Chris Lansdown 
I suppose my issue regarding the notion that “nonbelief in P does not imply belief in -P” is that this is an assertion, and as such, it requires substantiation. For the claim to be true, it logically follows that belief in a given proposition (in this case, theism) would result in a unique brain state, (call it B1) belief in the antithetical proposition (in this case, belief that no god(s) exist, gnostic atheism, or what some call antitheism) would result in another unique brain state, (call it B2) and most importantly, nonbelief in either proposition would result in a unique brain state that is neither B1 nor B2. Thus, the self-identifying atheist is obliged to provide evidence to support the claims that a distinct brain state of nonbelief in either of a pair of dichotomous propositions exists in reality, that atheism is such a state, and that he or she is actually in that state.
I have yet to see evidence to support any of those claims. Since according to Hitchens’ razor, what can be asserted without evidence can be dismissed without evidence, and according to Clifford’s principle, it is wrong to believe anything on insufficient evidence, one is justified (and arguably obligated) to dismiss the claims wholesale and proceed as if nonbelief of a proposition does imply belief in its antithesis. After all, as a/gnosticism pertains to knowledge rather than belief anyway, one can easily believe a proposition without (claiming) knowledge as to its veracity.
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