OK its raining and I am bored mind wandering as it does. You are on expedition in the Arctic with your best, very best mate, you know the one who will give you a reach round if the misses ain't about, there are only 2 Polar bears left in existence, one male one female. The female Polar bear attacks . Its clear that you have 2 choices, kill the Polar bear before he kills your best mate, knowing that in killing the Polar bear you are finishing the species for good. Or let the Polar bear kill your best mate because well there are billions of people on the earth and you can surely find another best mate. What would you do?