The attempt of religious believers to understand what atheism is has led many people to have misconceptions about what it entails. I recently went on Facebook and was confronted with an argument/arguments which belies atheism, and science in general. The belief expressed in the Facebook post was that the logical conclusion to an atheistic evolutionary worldview is that we would all be stabbing and raping each other, and simply doing everything we can just to survive. (Additional details about the post are at the end of my question in case of confusion)
The conclusion this person is implying is that because we do not live in such a world of violence, we must be relying on the morality of god. This claim seems clearly rediculous to me, yet to many believers it appears cogent. My question is about how to represent this argument in a formal deductive style.
Here I will present two propositions i think are involved in the confusion. The first proposition A is my rendition, and the second proposition B is a configuration that I am tacitly assuming an interlocutor might use.
Proposition A:
1- If we are acting in accordance with, and rely on, the morals given to us by god, we would not be stabbing each other.
2- We aren't stabbing each other, therefore we are acting in accordance with, and rely on, the morals given to us by god.
Proposition B:
1- If we aren't running around stabbing each other, we are reliant on the morality of god.
2- we aren't running around stabbing each other, therefore we are reliant on the morality of god.
Proposition A is clearly circular and what is called affirming the consequent. But when it is reconfigured into proposition B, the problem goes away. I feel like this argument is unprovable, and furthermore, it seems similar to saying that if you have a headache, you have a brain tumour. My question is, how does one refute this argument, particularly proposition B. Where did I go wrong?