Since theistic religions first began, there have been many arguments made by non-theists against the existence of God. When people refer to arguments for or against the existence of God, these arguments almost always refer to (a) a classical Biblical view of God, in which God is anthropomorphic, or (b) any view of God in which God is portrayed as omniscient, omnipotent and omni-benevolent (all-good). Most Jewish and almost all Christian views of God fit these definitions.

It is also worth noting that some atheists deny that arguments against the existence of God are necessary to support or sustain atheism. They argue that the burden of proof is on the person who makes the positive claim. It is not up to atheists, then, to prove that God does not exist; it is up to theists to provide proof of their own. Without such proof, atheists argue, it is not rational to believe in the existence of God, any more than it is rational to believe in the existence of fairies, dragons, demons or unicorns.

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