My question is about the relationship between God, determinism and ethics.
In my opinion if there is no God, then it looks like people do not have any non-physical "soul". I think most people would agree with this, partly because people usually reject God in favour of a naturalistic worldview in which the soul similarly has no place.
But if people do not have any "soul" then that must mean that that people do not have free will, because they are entirely physical.
But if people do not have free will then I don't understand how any ethics could exist, because ethics surely requires that people can choose.
So, if this is correct, then if you want to argue for some kind of ethics, then you have to accept the existence of God. But there is clearly an endless amount of Philosophers who don't believe in God and do argue for some kind of ethics, such as David Hume or Bertrand Russell. But how can they do this?
What I think you will say is that maybe ethics can exist even without free will. But surely this...
Most of your question is an excellent formulation of a major philosophical issue: whether minds, if they are merely parts of the general causal order, can possibly have the sort of authorship of their actions that would be required to hold them responsible---how can right and wrong get a foothold if we're just machines? Some say there's no problem here; others are more concerned. Rather than attempt a paltry paragraph on current views about this, let me point you to Timothy O'Connor's article in the Stanford Encyclopedia. One thing I will say, though, is that it is not clear that the worry would be lessened if it turned out that our minds were immaterial "souls". Souls would have to work somehow or other---a full ("God's-eye") understanding of their workings would presumably involve an inventory of the various states, structures, and processes that souls host, together with the "supernatural laws" that describe how these change over time. These laws might be deterministic or indeterministic,...