I want to clarify the problems with determinism under atheism. (Please notice how I define atheism).
Thankfully, Sam Harris has already identified one of the problems for us:
What most people overlook is that free will does not even correspond to any subjective fact about us. Consequently, even rigorous introspection soon grows as hostile to the idea of free will as the equations of physics have, because apparent acts of volition merely arise, spontaneously (whether caused, uncaused, or probabilistically inclined, it makes no difference), and cannot be traced to a point of origin in the stream of consciousness. A moment or two of serious self-scrutiny and the reader might observe that he no more authors the next thought he thinks than the next thought I write.