What is the syntactic role of "to do something" in these sentences?

Question

Take these sentences:

I felt he was mean to do that.

We'd be stupid to do something like that.

I feel like the "to do that" part in them functions differently syntactically than in sentences like "It is mean to do that" where "to do that" seems to be an infinitive clause functioning as the subject. Is "to do that" a complement to the adjectives "mean"/"stupid"?

Comparing "he was mean to do that" and "he was mean for doing that", I think semantically the two sentences seem close but still different, but I can't put my finger on how exactly they are different in meaning. So how are they different? Also do "to do that" and "for doing that" function the same way syntactically? Are they both complements?

Answer 1

From the diagram, it clearly show the difference

Answer 2

We'd be stupid to do something like that.

Answer 3

The adjective licenses a to+infinitive clause as complement.

She'd be reluctant to sing in front of a crowd

We'd be eager to engage your services.

Whereas this sentence:

He'd be stupid to say that to the judge.

could be construed as

He would be stupid (if he were) to say that to the judge.

and

He would be mean not to invite them to the party.

could be construed in the same manner:

He would be mean (if he were) not to invite them to the party.

Answer 4

Syntactially, to do that functions as an adjunct, not a complememt. For the sake of simplicity, we can reduce the given sentences to the following:

[i] He was mean to do that.

[ii] We'd be stupid to do that.

These adjuncts restrict the domain to which the rest of the clause applies - [i] does not imply that he is or was mean as a rule: it might be that he is a very nice person generally. The property of being mean is ascribed to him only with respect to this action. Similarly, [ii] does not imply that we would be generally stupid, but only as far as this single act would be concerned.

They can be shown to modify the entire clause as they do not form a unit with the predicative adjectives, and thus cannot be used as a unit as post-head modifier in a noun phrase.

*[The man mean to do that] was my brother.

Further, this clause resists most changes, becoming unacceptable in a non-finite form.

*(Him) Being mean to do that, I broke off relations with him.

*I planned for him to be mean to do that.

In fact, even changing the verb leads to a defective result.

?He seemed mean to do that.

?We'd look stupid to do that.

Note that with the extraposed subject version of these, this would be allowed.

It seemed mean (for him) to do that.

It'd look stupid (for us) to do that.

Considering the resistance of this structure to change, it might be best to consider it idiomatic: the use of a to-infinitival as an adjunct of domain is rare otherwise.

Comparing for doing that to the above, it produces about the same range of acceptability.

He was mean for doing that.

*The man mean for doing that was my brother.

?Him being mean for doing that, I broke off relations with him.

?I planned on him being mean for doing that.

?He seemed mean for doing that.

Answer 5

It is mean to do that. The infinitive phrase "to do that" is an appositive of it.