This paper will argue the following points. 1) What is a semantic status of prepositional phrases in such sentences as "Tom is good at tennis, " "It is wise of Tom to go there, " "This book is easy for John to read. "? 2) What is the semantic status of to infinitive (henceforth, to VP) in the following sentences : "He is honest to bring back the money," "He is sure to win." 3) Is there a semantic difference in such sentences as "It is wise of Peter to go home ", "Peter is wise to go home?" If there is any, what is it? 4) What is the predicate?argument structure of a sentence containing a predicate adjective like "John is easy for Mary to please?" Is it one-place, two-place or three-place-structure? 5) By introducing the notion of a predicate modifier we can solve these problems. 6) We conclude that adjectives are simply a one-place predicate.