Using the phrase “just in case” as synonymous with “if and only if” is rampant in contemporary philosophy. I remember it first coming up explicitly in one of my logic classes as an undergraduate. The professor said that we should translate the English phrase “just in case” as “if and only if” (or its symbolic equivalent, “<–>”). Since we were supposedly talking about ordinary English, the students got to objecting to the professor’s translation rule. We insisted that in English “just in case” is only used as it is in the phrase “She built a storm shelter just in case a terrible storm came through town.” The professor was dumbfounded.
Well, so was I. Yet for as long as I’ve been studying philosophy, I’ve still been puzzled by it. But I’ve pretty much just put the issue on the backburner. My best guess has been that I’m not crazy, this is a technical turn of phrase used by philosophers (and perhaps other academics), and the professor had just gotten so wrapped up in that usage he lost touch with ordinary English. But I’ve always wondered whether this non-ordinary use is something philosophers really recognize as such. Could it be that young philosophers just assume it’s an ordinary phrase of English that only the highly educated use (and thus they follow suit)? After all, I have never heard it introduced as a special term, despite its ubiquity in philosophy classrooms.
I’ve discussed this issue with other graduate students in philosophy from time to time, but no one seemed to know much about the origin of this odd (I think) use. I got to thinking about this issue again today and did a bit of Google searching to shed light on it. I found this post by a linguist, Geoffrey K. Pullum:
He seems as puzzled as I am and draws pretty much the same conclusion that I had: it’s an (American) academic invention. But I wonder what others think, especially those within philosophy. Anyone know anything about this?