How About THIS Morals -Ethics Question?

[David Sklansky]

You are brought at gunpoint into a laboratory where you will be forced to choose which of two rooms will have those in it killed painlessly. If you refuse they all will be, so let's not even contemplate that option.

In one room is a very elderly person you have never met. In the other is your devoted three year old collie. Can sparing your collie be justifed by any respected philosophies? What about any respected religions?