 But the most influential objection to supervenience physicalism (and to modal formulations generally) is what might be called the sufficiency problem. This alleges that, while (1) articulates a necessary condition for physicalism it does not provide a sufficient condition. The underlying rationale is that, intuitively one thing can supervene on another and yet be of a completely different nature. To use Fine’s famous (1994) example, consider the difference between Socrates and his singleton set, the set that contains only Socrates as a member. The facts about the set supervene on the facts about Socrates; any world that is like ours in respect of the existence of Socrates is like ours in respect of the existence of his singleton set. And yet the set is quite different from Socrates. This in turn raises the possibility that something might be of a completely different nature from the physical and nevertheless supervene on it.