 Now let us say that a clause is left-redundant if it is possible to tell by looking at the material in the sentence to the left of the clause that the clause is redundant. So “Mary owns an animal” is not left-redundant in (28) (except if the context of utterance already entails that Mary owns an animal), because there is no material before that clause, implying that it is impossible to tell by looking at material to the left of the clause that the clause is redundant. On the other hand, the same sentential fragment, “Mary owns an animal”, is left-redundant in (29) and also in (20):