You, your spouse, and your young child are walking on an empty street at night.

You turn a corner.

A man stops you and points a gun at your spouse’s head.

His finger is squeezing the trigger.

You have this folding knife in your pocket.

The blade is less than three inches long; with one quick movement you have practiced before, you can pull the knife from your jacket pocket and flick the blade into performance with your thumb and embed it in his throat faster than he can finish pulling the trigger.

If you decide to pull the knife, the only option is to kill the man.

Threats and wounding will only result in the death of your spouse and child.

Do you pull the knife or not?

If yes, why? If not, why not?

Where do you cut the line on killing?

Does it begin and end with a life in the balance?

What if the same person with the gun had instead completely soaked your house in gasoline and was in the process of striking a match to engulf your home in flames?

Is that enough of a threat to health and home to claw the threat into red with that knife in your pocket?

If yes, why? If not, why not?