Learn how to explicitly indicate the “logical subject” that performs the action of an infinitive. The distinction between for and of is a frequently tested point.
Basic Rules
① for + objective case + to V: used in general cases. “It is important for students to review every day.”
② of + objective case + to V: used when the adjective expresses a person's character (kind / wise / foolish / clever / rude / careless, etc.). “It is kind of you to help me.”
Test: If it can be rephrased as “the person is ~,” use of (You are kind. → of); otherwise, use for.
③ want/ask/tell/advise + O + to V: O is the logical subject of the infinitive. “He told me to come early.”
It is natural for him to feel nervous.（It is natural that he feels nervous）← for
It was careless of her to make such a mistake.（She was careless to make such a mistake）← of
※ careless / kind / wise / foolish / clever / rude → of; other adjectives → for
Points to Remember
① Distinguishing for and of: “It is foolish of him to do so.” → “He is foolish.” is possible → of. “It is important for him to do so.” → “He is important.” is not possible → for.
② When the subject of the infinitive and the subject of the sentence are the same: In “I want to succeed,” I is the subject of the infinitive, so do not write for I.
③ Construction with introductory subject it: it refers to the infinitive phrase that follows (the real subject). “It is impossible for robots to feel emotions.”
- for + O + to V: a general logical subject
- of + O + to V: used with adjectives describing a person's character (kind / wise / foolish / rude / careless)
- Test: use of if “the person is ~” is possible
- With want/ask/tell + O + to V, O is the logical subject of the infinitive
Practice
- Translate “It was careless of him to be late” using It is ... of ... to ...
- Fill in the blank: It is necessary ___ you to submit the report by Friday.
- Correct the error: It was wise for him to keep silent at that moment.