Can I use would have alone like
The situation would have been worse without his help.
The lack of anybody's cooperation would have caused us a lot of problems.
to provide the same meaning as using the third conditional (unreal past situations) like
The situation would have been worse if he hadn't helped us.
?
I've seen this use with other modal auxiliary verbs such as could have, must have in a grammar book. But I couldn't seem to find would have used alone in the book. So I would like to ensure if this is the correct use of perfect infinitives. Detailed explanation would be much appreciated.
Best Answer
Yes, this is acceptable.
Both your sentences present conditionals; although they are not expressed as formal IF ... THEN constructions, they might easily be so:
The protasis (IF clause) of a conditional may lie outside the sentence at hand; this does not invalidate the use of would:
All of these uses are equally valid with non-past✲ reference:
In fact, most uses of would may be understood as implicitly conditional, though the actual condition implied may be very vague:
✲ I should perhaps note that past modal + have + past participle , although it looks like a “perfect” construction, has nothing to do with the ordinary English “perfect”. It is, rather, the language’s workaround for the awkward fact that the modals can, may, shall, will may be used in their “past” forms with non-past (present or future) reference—which leaves them no convenient form for expressing the same modality with past reference. To accomplish that, we employ the “perfect” construction. It would have been is in effect the simple past of It would be.