Atheism: A Lack of Belief in God

Introduction

I recently had a conversation on Twitter with an atheist. He held a particular view of atheism that made it quite difficult to have a productive conversation. This view has become more popular among internet atheists in the last few years, so I thought it would be worth addressing. 

What is Atheism?

This atheist immediately began our interaction by questioning my understanding of atheism. He claimed that atheism did not make the claim that God does not exist (as is the traditional understanding), rather it is neutral on God's existence; it does not make an ontological claim (if God exists) but rather an epistemological claim (if someone believes that God exists). He rationalized this untraditional understanding by saying that since theism is the belief in God, then atheism is the denial of the belief in God, but it is not necessarily the denial of God's existence. After I asked him a few clarifying questions, he claimed that no one could really "know" that God exists and we are all actually agnostics. He ultimately claimed that atheism is indistinguishable from agnosticism. 

Burden of Proof: A New Perspective?

I was thinking the other day about the burden of proof. It seems that no one wants to bare it. Many atheists claim that they don't shoulder the burden of proof because "you can't prove a negative". Some theists claim that they don't hold it because you can't prove something that is metaphysical (based on the assumption that only things that can be decisively measured can be "proven").