Where in the literature do we find the preferred formal definition of “proexample” as in: the number zero is a proexample for the existential sentence "some integer is neither positive nor negative"? The notion of proexample is a kind of dual to counterexample. A universal sentence is false iff it has a counterexample. An existential sentence is true iff it has a proexample.
Where in the literature is the notion of “proexample” formally defined? And what are the main theorems involving this notion? And what questions concerning it remain open?
I was quite surprised to find that "proexample" is actually a word. Google turns up, for example (or should that be "for proexample"?) Corcoran, J. 2005. Counterexamples and proexamples. Bulletin of Symbolic Logic 11(2005) 460.
Are you that John Corcoran? If so, you seem to be the main published user of this word, so you are the one who should be answering this question.