In this paper, we show that many of the dramatic changes that took place in the course of the history of the English complementation system are the result of a simple morphological Change in the determiner system. We propose that Old English (OE) evolved from a system in which 'complements' clauses, relative clauses and DP were interpreted as adverbials to a system in which they are interpreted as arguments of the verb. As the determiner acquired certain certain type of morphological feature , a complementation system developed. We show that this claim is is reinforced by the fact that apparently unrelated changes all follow from the nature of the determiner system.