 While a number of authors have noted that presuppositions behave in some respects like anaphors (e.g., Kripke 2009 and Soames 1989), it was van der Sandt (1989; 1992) who brought out the connection the most forcefully. He noted that for every configuration of anaphors and antecedents where a pronoun is interpreted anaphorically but is not interpretable as a bound variable, a similar configuration is possible with  presuppositions.[13]  In each of the following quadruples, we illustrate some configuration in the (a) and (b) examples, while the (c) and (d) cases show that a slight divergence from the original configurations (i.e. those in (a) and (b)), produces infelicity. Note that the (a) and (c) examples include an anaphoric pronoun (“it”), and the (b) and (d) examples include the factive verb “knows”, which triggers a presupposition that its propositional complement is true (i.e., that Fred left). So, anaphora is felicitous in configurations in which presuppositions are felicitous, and anaphora is infelicitous in configurations in which presuppositions are infelicitous. It is clear that connections between anaphoric pronouns and their antecedents on the one hand, and presupposition triggers and their antecedents on the other, are sensitive to very similar configurational requirements.