 Regarding this last problem, Salmon 1992 and McKay 1991 compellingly argue that believing that Superman is stronger than Superman is distinct from believing that Superman is stronger than himself because the proposition that Superman is stronger than Superman is different from the proposition that Superman is stronger than himself, on the grounds that being stronger than Superman is a different property from being stronger than oneself. The first is a two-place relation, with the identity pair &lt;SUPERMAN, SUPERMAN&gt; as relata; the second is a one-place, self-reflexive property. (For more on the difference between xRy and xRx, under an assignment of the same object to both variables x and y, see Fine 2007 