  The problem with Scotus’s argument, then, is this. The inferences from 4 to 5, and from 6 to 7, are valid only upon the assumption that if a cause is sufficient to produce an effect no other cause is a necessary condition of that effect. But this is true only if a causally sufficient condition is such that it alone suffices to produce its effect, that is, if it is causally sufficient in the strong sense. If “causally sufficient condition” is taken in the strong sense, however, there are reasons to believe that the argument’s first premise is false. Suppose, for example, that Abel would exist if and only if Adam and Eve were to freely copulate, and Adam and Eve would freely copulate if and only if God were to create them. By creating Adam and Eve, God brings about Abel’s existence. Furthermore, given the truth of the relevant subjunctive conditionals, there is a clear sense in which God’s doing so is not only a necessary but also a sufficient causal condition of Abel’s existence. For if God creates Adam and Eve, Adam and Eve will beget Abel. It isn’t sufficient in the strong sense, however, because God’s creating Adam and Eve won’t, all by itself, ensure Abel’s existence. For that to occur, Adam and Eve’s free decision to copulate is also needed. Theistic intuitions clearly support the claim that it is necessarily true that God’s creative volitions are a causally sufficient condition of the existence of every other concrete object in at least a weak sense. It is less clear that they support the claim that it is necessarily true that God’s creative volitions are a causally sufficient condition of the existence of every other concrete object in the strong sense. (Theists with robust views of human freedom, for example, will deny that they are.)