Suppose there's a reason, call him 'Randy', and it speaks in favor of pushing the red button. Suppose there's a reason, call her 'Griselda', and it speaks in favor of pushing the green button. Suppose it's impossible to push both buttons. Question. Does Griselda _also_ speak against pushing the red button? I'm not asking whether it could. I'm asking whether it _must_ simply in virtue of (a) that Griselda speaks in favor of pushing the green button and (b) you cannot push the green and the red.
I'm really not sure what to think. I can see Randy speaking in favor of pushing the red button without thereby speaking against pushing the red button and the same for Griselda. Of course, pushing the red means missing the opportunity to conform to the demands Griselda made. Pushing the green means missing the opportunity to conform to the demands made by Randy.
Here's a little argument that I _think_ is a decent little argument against the view that Griselda _must_ speak against pushing the red button. Changing examples should help. Jones is out for his morning constitutional when he sees a man fall into the river. Seeing that the man was struggling to pull himself out and is in serious danger of being pulled away from the bank, he rushes over to lend a hand. Smith is heading out to meet Jones the next day for lunch when he sees a different man fall into the same river. Seeing that this man was struggling to pull himself out and in danger of being pulled away from the bank, he rushes over to lend a hand knowing full well that his assisting this stranger would prevent him from keeping his appointment with Jones. Now, the strength of the case for Φ-ing is a function of both the reasons to Φ and the reasons to refrain from Φ-ing. It seems that the case for Smith to assist and the case for Jones to assist is equally strong. It follows that the reasons that favored keeping the meeting were not reasons to refrain from helping the man.
Thoughts? I first became interested in this issue when I was trying to explain Ross' view in class and it struck me that I wasn't quite sure whether Ross would say that the reasons associated with each of his prima facie duties _both_ asked us to perform acts of certain types and act against the other duties on the list. (Of course, he believed in real conflict but I don't think it is obvious that believing in real conflict and rejecting the specificationist view on which moral principles 'anticipate' each of the circumstances under which they fail to determine what ought to be done all things considered and treats them as exceptions you have to take a stand one way or the other.)