Evidence

In the case of debates about God, the burden is on the believer to offer support for her position if she wishes it to be considered seriously. In reality, the only necessary argument against believing in God is simply that there is no evidence that any gods exist. An atheist doesn't need to justify her lack of belief any further. This keeps the burden of proof on the side of the claimant where it belongs. The person making a claim has to provide the evidence for its validity. Would you believe in the claim that flying pineapples exist until proven wrong without any evidence? Probably not. You would withhold belief until there is evidence to support such a claim.

---Armin Navabi, in Why There Is No God---