grammar - to phrase... where is the noun it modifies?

1. She is not a person to fear.




2. She is not a person to be feared.

It is fine to use both forms, but I cannot catch the definite difference between them in meaning. Also, why is it OK to use both forms? It seemed to me that when there is "noun+to phrase" structure, this to phrase is linked to the subject. For example:

We didn't have anything to wear. (Who had nothing to wear? Us!)

But unlike this example sentence, the to phrase in sentence 1 implies that I or we are the people who should not fear her, which means that it's not modifying its subject "her", but other nouns that are not even in the sentence. The sentence itself makes perfect sense to me, but I don't know why it is. Can someone please explain why it is grammatically fine to use sentence 1 and the difference in meaning between those two sentences?

Answer

They are different structures.

Consider

She is to be feared.

but

*She is to fear.

(* means ungrammatical, or unacceptable).

From this you can see that to be feared is what is called a "small clause", the result of Whiz-deletion:

She is a person [who is] to be feared.

So she is the subject of that small clause, which thus has to be passive.

But the first form does not have this structure: She is a person who is to fear is probably not grammatical, but even if it is it doesn't have the same meaning. The to fear is a modifier on the noun person, and can't appear as a complement.

She therefore does not have to be the subject of fear; and if she were we would use a different structure again such as She is a fearful person or She is a person who is afraid, or She is a person fearing XYZ; so pragmatics leads us to interpret She is a person to fear as meaning that she is the object of fear.