Atheism and the Burden of ProofIn recent years there has been a lot of debate regarding the proper definition of “atheist,” even on this blog.  Traditionally, atheism has been defined as the claim that God does not exist. In the mid-20th century, however, atheist philosopher Antony Flew attempted to redefine atheism.  Noting that the Greek prefix “a” is a term of negation, Flew said the proper definition of a-theism is simply “not a theist.”  Another popular way of cashing this out has been to define atheism as “one who lacks belief in God.”

What’s the difference between these definitions?  The traditional definition is an ontological claim (God is not included among the entities that exist) while the new definition is a psychological description (“I have no belief regarding the existence or non-existence of God”).  We might label these two ways of defining atheism as  “ontological atheism” and “psychological atheism.”

Why does it matter how we define atheism?  It matters because of the burden of proof.  A principle of rational discourse is that he who makes a claim bears the burden to defend it.  If someone claims that God does not exist (ontological atheism), he bears a burden to demonstrate how he knows this to be true.  On the other hand, one who lacks any beliefs with respect to God’s existence (psychological atheism) bears no burden of proof because he is not making a claim to knowledge.  He is merely describing the content of his beliefs – that his stock of beliefs does not include a belief regarding the existence or non-existence of God.  Flew understood this.  He purposely redefined atheism to make it a psychological description so as to absolve atheists from their burden to defend the claim that God does not exist.