A "meta-argument" against all future arguments for God's existence ?

[Belacqua]

What do you consider the soul to be?

The standard meaning of "soul" in Western philosophy was defined by Aristotle and adopted later by the Christian church. For them, it has a specific meaning. Obviously you're free to define it however you like, but then you'd be talking about something different.

For Aristotle and for Christians, the soul is the form of the body. "Form" here doesn't mean just "shape," because a newly-dead body has the same shape but no soul. As always in Aristotelian hylomorphism, "form" refers to the shape of the parts, their function and interaction. How they work, what they do. 

Souls always give form to matter. The matter of the body is carbon, calcium, hydrogen, etc. The way this matter is put together, to make it into the unique thing that it is, is the form -- the soul. 

Therefore souls are not material, but always exist with matter. Matter always has a form, form can't exist without matter. 

This is why Paul doesn't say that after death the soul will fly away immaterially. He says that the same soul will go to new matter. This is the part of Christianity that demands supernatural belief. We can all agree that bodies have forms, but not that the same form can somehow go to new matter. Aristotle didn't think this was possible, either. 

And if you don’t like the word “soul”, just replace it with the word consciousness. Where does consciousness come from?

Again, if you choose to say that "soul" and "consciousness" are synonymous, no one will stop you.

Traditionally, however, consciousness is one of the activities of the body made possible by the fact that the body is put together in a certain way -- the form, the soul. Soul is responsible for more than consciousness, however. It's also responsible for all the unconscious processes, and everything that makes a person a person.