On September 10 2008, the large hadron collider was finally switched on.  It is a machine that is at the cusp of human knowledge and endeavour, it will enable humanity to understand the universe and provide knowledge of benefit to all people, living and of the future.

However, tragically, a person was killed in the construction of the machine.

The dilemma is this.  If you were the chief engineer of the project, and you were told in advance of starting construction that it was a certainty that one person would be killed, would you still continue with the project?

How about if the chance of one person dying was 75%?

or 50%?

Or unknowable?

3a

A trolley (tram) is running out of control down a track. In its path are five people who have been tied to the track by a mad philosopher. Fortunately, you can flip a switch which will lead the trolley down a different track. Unfortunately, there is a single person tied to that track.

Should you flip the switch?

3b.

As before, a trolley(tram) is hurtling down a track towards five people. You are on a bridge under which it will pass, and you can stop it by dropping a heavy weight in front of it. As it happens, there is a very fat man next to you - your only way to stop the trolley is to push him over the bridge and onto the track, killing him to save five.

Should you push him?

3c.

As before, a trolley(tram) is hurtling down a track towards five people. As in the first case, you can divert it onto a separate track. On this track is a single person. However, beyond that person, this track loops back onto the main line towards the five, and if it weren't for the presence of that person, who will stop the trolley, flipping the switch would not save the five.

Should you flip the switch?

2. The Plank of Carneades

There are two shipwrecked sailors, A and B, treading water in the middle

of the ocean. They both see a plank that can only support one of them

and both of them swim towards it. Sailor A gets to the plank first.

Sailor B, who is going to drown, pushes A off and away from the plank

and, thus, ultimately, causes A to drown. Sailor B gets on the plank and

is later saved by a rescue team.

Can Sailor B can be tried for murder?

1. The 'famous violinist' thought experiment:

You wake up in the morning and find yourself back to back in a hospital

bed with an unconscious famous violinist.

He has a fatal kidney ailment, and you alone have the right blood type

to help. You have been kidnapped, and the violinist's circulatory system

has been plugged into yours, so that your kidneys can be used to extract

poisons from his blood as well as your own.

To unplug you would be to kill him. He needs to be attached to you for

only nine months. By then he will have recovered from his ailment, and

can safely be unplugged from you.

What do you do?