This question was prompted by a friend who is a fluent speaker of English but not a native one.
Consider the following cases:
- I either eat the apple or the orange. I eat: apple XOR orange.
- I eat either the apple or the orange. I eat: apple XOR orange.
- The banana either costs more than the apple or the orange. banana > apple XOR banana > orange
- That is: The banana costs more than the apple or the orange, but not both.
- The banana costs more than either the apple or the orange. banana > apple AND banana > orange
- That is: The banana costs more than both the apple and the orange.
My friend asked me, as a native speaker, to first confirm that this was the correct logical translation and then to explain just what the hell is going on here. What rule governs the distinction in the second pair of propositions?
Usually in these cases, I just explain it away as some form of idiomatic expression: "Sometimes either/or means exclusive-or and sometimes it means and. It's just the way it works."
However, I did notice one thing here. This distinction arises in the propositions involving a comparison between subject and objects: less than or more than.
Am I on to something? Anybody have a more coherent explanation?