This paper analyzes the diachronic change of complement form from the that-clause into the to- infinitive clause, which is headed by a deontic predicative adjective. The rise of to-infinitive clauses and the decline of that-clauses from ME seemed to be caused by analogy and assimilation between verbal and adjectival mandative constructions. The analogical change was triggered by language internal factors such as the loss of inflections, word order reanalysis and the development of control construction as well as the principle of event integration and clause union, complexity principle and accessibility theory. In the deontic adjectival complement clause, the toinfinitive clause has been keeping roughly 3:1 to the that-clause from ModE up to PDE. In addition, adjectival complements with to-infinitives have shown less abrupt and more constrained than verbal complements with to-infinitives. Such developmental process is related to the constraint on the syntactic operation that substitutes to-infinitive clauses for that-clauses. In fact, the that-clause could be changed into the to-infinitive clause only if the thatclause functions as a logical subject in the deontic adjectival complement clause. Futhermore, deontic adjectives can't be merged with an animate subject since predicative adjectives of this type don't connote subject-oriented activity.

• 박상수(부산외국어대학교)