 The modern treatment of presupposition has followed Frege in treating survival under negation as the most important test for presupposition. That is, if it is implied that p, both in an assertion of a sentence s and in an assertion of the negation of s, then it is presupposed that p in those assertions (unless that p is entailed by all sentences). Other typical examples of presupposition (Levinson 1983: 178–181) include