原則1: Object機能の完全否定
Modern English Grammar では to-infinitive は決して Object の機能を果たさない
"I want to go" → "to go" = Catenative Complement (NOT Direct Object)
"I want him to go" → "him" = Direct Object, "to go" = Catenative Complement
"I teach him to swim" → "him" = Direct Object, "to swim" = Object Complement
原則2: 「名詞的用法」概念の完全否定
Modern English Grammar では「to-infinitive の名詞的用法」という概念は存在しない
Traditional: "to-infinitive の名詞的用法"
Modern: "to-infinitive phrase が特定の機能を果たす"
原則3: Category vs Function の厳密区別
Category（語類）と Function（機能）は完全に別概念
Category: to-infinitive phrase（独自のカテゴリー）
Function: Subject, Complement, Adjunct（文中での役割）
"To be happy is important" → Category: to-infinitive phrase, Function: Subject
原則4: Subject機能は可能
to-infinitive phrase は Subject の機能を果たすことができる
"To learn English is difficult" → "To learn English" = Subject (”名詞的用法”ではない)
• • "To be or not to be is the question" → "To be or not to be" = Subject