[quote="johnmann, post:19, topic:323110"]
It's not that unusual. We fulfill an anticipated obligation whenever we attend a vigil.
Ahh, but that's different. That's an obligation that already binds, and we're fulfilling it early. In this case, we've got a 'non-obligation' -- something that doesn't yet bind (unless and until he returns in time) -- and an attempt to fulfill an obligation that doesn't yet exist! ;)