Infinitive as adjective clause

They look the same to me.

Here are some ways of analyzing your sentences.

I was a fool to believe her.

Infinitive with adverbial function. Answers the question "Why?" I was a fool because I believed her.

I was the first man to win the championship.

Infinitive with adjectival function. I was the first among the men who would win the championship.

C

(1) I respectfully agree that the infinitive phrase is adjectival and modifies "fool."

(2) Some grammarians suggest that adjectival infinitives are just a short way to express an adjectival/relative clause.

(3) Possibly some people would suggest that the "full" sentence might be something like: I was a fool who believed her.

(4) One authority (who, of course, could be

AnonymousOne authority (who, of course, could be wrong) has suggested a test to determine whether an infinitive phrase is adverbial or not. He says to put "in order" in front of "to." If it makes sense, then the infinitive is adverbial.

You may recall from logic class that this can be true without implying that if it doesn't make sense then the infinitive i

Thank you for your insightful answer. You have certainly given us all food for thought. I shall study your arguments carefully. And continue trying to find other opinions. Hopefully, other people will join this thread.

Debpriya De:

(1) I have researched your intriguing question some more and hereby present my conclusions for your consideration:

(a) Mr. CalifJim is correct: "to believe her" is being used in an adverbial sense.

(b) Here are some paraphrases that I have been able to find (the first two are Mr. CalifJim's):

(i) I was a fool because I believed her.

(ii)