Arguments against the existence of God
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 claims the existence of an entity. 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. The nonexistence of these creatures is not proven, yet it would be absurd to gamble on their existence. This argument is favorable to both weak atheism and agnosticism. It should be noted that this form of disbelief in the existence of God is not necessarily an active denial of God's existence, but more a sort of "disbelief by default." The Argument by Ockham's Razor is the most prominent example of this kind of disbelief.
The active denial of God's existence can be approached in two different ways. One is to attempt to develop an argument showing that the existence of God results in a logical contradiction, a proof by contradiction; many of the arguments above take this approach. The other approach is to deny the existence of God as a matter of faith, which can carry a burden of proof analogous to that borne by those who assert God exists based on faith.
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