Some methodological atheists formulate the principle by saying that the burden of proof is always on any person making an existence claim, since, from a logical point of view, existence claims are only capable of proof, not disproof. No one has ever proven the nonexistence of Santa Claus, or elves, or unicorns, or anything else, simply because the very logic of an unrestricted existential proposition prohibits its disproof. It is impossible to go all over the universe and show that, for example, there are no elves anywhere. For this reason, rational methodology calls for us to deny the existence of all those things which have never been shown to exist. That is why we all regard it rational to deny the existence of Santa Claus, elves, unicorns, etc. And since God is in that same category, having never been shown to exist, it follows that rational methodology calls for us to deny the existence of God.