Motivated by this question I've realised I have some difficulty in interpreting infinite clauses.
What is an infinite clause?
One of my grammar books says that an non-finite clause is a dependent clause that unlike finite clauses have no tense or modality. Infinite clauses are a particular case of non-finite clauses, and are constructed using a verb in infinitive form. Here are some examples:
To have thought this made him more cheerful
It's difficult to maintain a friendship
My goal now is to look into the future
My difficulty: Attaching a tense to an infinite clause
Probably because of the *-to-be expressions:
I have interpreted clauses like:
then to be seen only in Japan
which are about to be seen only in Japan
In the question I linked above, @StoneyB points out that correct interpretation is:
which then could be seen only in Japan
My question: Do infinite clauses with perfect aspect imply a past tense?
I would like to get help to interpret the difference in meaning in these two clauses:
To think this makes him more cheerful
To have thought this makes him more cheerful
Amber already answered to this question in the comments:
You find it unthinkable that this makes him more cheerful.
You thought this would make him more cheerful, but in retrospect it seems unthinkable.
Additional question: Can an infinite clause carry meaning of future
I understand from Amber's comment that "to think" just describes the action of thinking without saying when, but "to have thought" describes a past event, a thinking I did in the past.
What I would like to see is whether there are cases where "to think" may carry meaning of a future action, as in the expression is-to-be.