Evolutionary theory, in its application to finite populations of organisms, is a probabilistic theory. To understand more precisely what is involved in the biological claim that mutations are unguided, this chapter considers a simple experiment. The experiment involves a large number of blue organisms so that one gets mutation frequencies different from zero. If the existence of guided mutations doesn't show that God exists, then the nonexistence of guided mutations doesn't show that God does not exist. Atheists and theists should agree that the biological question is separate from the theological question. The chapter suggests that Pierre Duhem's thesis provides a good model for how biological findings about mutation are related to theistic claims about divine intervention in the mutation process. Some versions of interventionist theism, like Young Earth Creationism, are logically inconsistent with evolutionary theory. The idea that God sometimes intervenes in the mutation process is different.