Sentences such as
To think that she did all that
To think that Messi and Cristiano Rolando are both out of the World Cup
To think that this could ever happen to me
Are these impersonal sentences (i.e. the infinitives have no subject) or are these sentences that have implicit subjects (because it's understood that "to think" requires someone to do the "thinking")?
My instinct tells me that they have implicit subjects; however, I can't add the implied subject (for example, I can't say For me to think that she did all that, or at least it sounds odd to me). It seems that these sentences, as written, reject overt subjects; why is that, and does that make such sentences impersonal?
Thanks in advance