If you can say "I think him a great man.", can you also say "I think him great."?
2 Answers
Both those sentences are correct (if a bit old-fashioned). However, they don't convey the same meaning, simply because He's great. does not convey the same meaning as He's a great man.
He's great
This is an informal/colloquial construction which implies wonderful; first-rate; very good.
He's a great man
This, on the other hand, implies a person who has achieved importance or distinction in a field.
One might say, "John always helps me out with my homework. He's great!" And it would be perfectly okay, because it would convey that the speaker thinks John is wonderful for helping him out.
But if one was to say that "John is a great man", it would imply he has done something important or impressive - helping one with homework wouldn't be enough!
Yes. Most common is "I think that he is a great man", less so is "I think him a great man", least common is "I think him great."