It is commonly thought that theism entails full religious observance and that atheism entails either the abandonment of religious practice or, at least, its reform. Focusing on Judaism, I argue against both of these entailment claims. Both theistic departure from religious observance and atheistic adherence to religious practice are coherent. I outline the features of those religions that make them more conducive to atheistic observance. Finally, I consider various objections to full observance by atheists.