infinitive as attribute

[Clark]

I can't work out the difference between an active and a passive infinitive in the attributive function in some sentences.

E.g. He is a man to trust. vs. He is a man to be trusrted.

Could you help me?

[David L.]

He is a man to trust. vs. He is a man to be trusted.


These may not be the best sentences to discuss your query.
A native speaker would say either, He is the man to trust. (for this particular job)


He is a man you can trust
This has the same meaning as

He is a man to be trusted. ( in general, whatever the situation, now and in the future, a trustworthy man)

Let's keep going because I doubt that this really gets to the heart of your uncertainty.

[Clark]

He is a man to trust. vs. He is a man to be trusted.


These may not be the best sentences to discuss your query.
A native speaker would say either, He is the man to trust. (for this particular job)


He is a man you can trust
This has the same meaning as

He is a man to be trusted. ( in general, whatever the situation, now and in the future, a trustworthy man)

Let's keep going because I doubt that this really gets to the heart of your uncertainty.

Yes, the picture is still vague.
At first I thought that passive infinitive implies only the modality of necessity. Now I understand it is not quite so.
e.g. He is a man to be trusted. (possibility)
There are still many things to be done. (necessity)

Could it be that active infinitive always suggests that the modified noun should have a specifying determiner, like the definite article?
e.g. He is the man to rely on.
Then is it correct to say 'He is the man to be relied on'?

[David L.]

He is the man to rely on.
Then is it correct to say 'He is the man to be relied on'?

No. It is:
He is a man to be relied on.
He is a man you can rely on.
He is the man we can rely on.

Can you explain your query in simpler words than "passive infinitive implies only the modality of necessity" ?

[Clark]

He is the man to rely on.
Then is it correct to say 'He is the man to be relied on'?

No. It is:
He is a man to be relied on.
He is a man you can rely on.
He is the man we can rely on.

Can you explain your query in simpler words than "passive infinitive implies only the modality of necessity" ?

Too many big words, I agree.
There are still many things to be done (= that must be done). 'Must' is a modal verb that expresses necessity in this sentence. Consequently, the infinitive 'to be done' implies the modality of necessity.

However, it looks the distinguishing feature between active and passive infinitive in this function has nothing to do with modality, but is related to whether the attribute expressed by this infinitive is limiting or descriptive. To put it plainly, it depends upon whether we have 'a' or 'the' before the modified noun.
e.g. This is a book to be read. (correct)
This is a book to read. (incorrect)
This is the book to read. (correct)
This is the book to be read. (incorrect)

Am I right in my conclusions?

[Soup]

I can't work out the difference between an active and a passive infinitive in the attributive function in some sentences.

E.g. He is a man to trust. vs. He is a man to be trusrted.

Could you help me?

This is a very cool question.


Passive / verb structure
He is a man to be trusted.
=> by us; who we can trust <there is a subject>

Absolute / nominal structure
b) He is a man to trust.
=> he is trustworthy <there is no other subject>


Note, 'a man' and 'the man' are grammatically correct but express difference meanings, general vs specific.


This is a book to be read.
This is a book to read.

This is the book to read.
This is the book to be read (on summer vacation).

[Clark]

This is a very cool question.


Passive / verb structure
He is a man to be trusted.
=> by us; who we can trust <there is a subject>

Absolute / nominal structure
b) He is a man to trust.
=> he is trustworthy <there is no other subject>


Note, 'a man' and 'the man' are grammatically correct but express difference meanings, general vs specific.


This is a book to be read. (1)
This is a book to read. (2)

This is the book to read. (3)
This is the book to be read (on summer vacation). (4)

(1) = This is a good book for us to read.
(2) = This is a good book for anybody to read.
(3) = This is the best book for anybody to read on summer vacation.
(4) = This is the book for us to read on summer vacation.

Is my interpretation too straightforward?

[Soup]

(1) = This is a good book for us to read.
(2) = This is a good book for anybody to read.
(3) = This is the best book for anybody to read on summer vacation.
(4) = This is the book for us to read on summer vacation.

Is my interpretation too straightforward?

They're all grammatical. Notice the object of the for-phrase 'us' isn't the structural subject of the infinitive phrase. Moreover, that you can move the for-phrase because is functions disjunctively:

For us, this is a good book to read.
This is, for us, a good book to read.
This is a good book to read, for us ~ to us.

[Clark]

I wanted to emphasise the doer of the action. From what you write that is the key factor that distinguishes active and passive infinitives in these constructions.

[Soup]

I wanted to emphasise the doer of the action. From what you write that is the key factor that distinguishes active and passive infinitives in these constructions.

Right. The doer of the absolute phrase is provided by "for us". With passive constructs, on the other hand, the subject is implied:

Ex: This is a book to be read (by you) over summer vacation. <requirement; command>

Ex: This is a book to read over summer vacation. <suggestion>

Ex: This is a book for you to read over summer vacation.