Unbreakable Vows

[Bart Lidofsky]

No: HPFGUIDX 165535

Bart:
There is not a lot of canon here, so I am basically using logic. I will, however, outline the logic I am using:

1) The Unbreakable Vow is a fairly well-known spell (at least Ron's comments/story and the fact that it was assumed that Snape would be familiar with it implies this). 

2) Useless spells would not generally become well-known, except perhaps for their uselessness.

3) Therefore (first conclusion): The Unbreakable Vow is a useful spell. 

4) If someone breaks the Unbreakable Vow, it causes death (we only have hearsay for this, but there must be SOME reason why it's called the Unbreakable Vow. We can assume that breaking it is either physically impossible, or has very dire consequences.

5) Assumption: No sane person would make an Unbreakable Vow if they don't clearly understand what it is they are vowing to do.

6) Therefore (second conclusion, combining #3 and #5): The vow is what the person making the vow understands it to be. 

7) This would imply that the Unbreakable Vow is only triggered if the person who had made the vow believes that he or she has broken it. 

Given this (and if you disagree, feel free to show flaws in my logic), what do you think SNAPE was thinking he was vowing to do at Spinner's End?

Notes: What happens when an unbreakable vow is unachievable due to changing of circumstances? How unbreakable is it? Can the person to whom the vow was made agree that the vow has been kept, when it hasn't? 

Examples:
A) I make a UV to take someone to dinner at Windows on the World restaurant for a special occasion (meaning a specific date). Unfortunatetly, it was destroyed in the 9/11 attack, making it physically impossible for me to keep the vow, although there was no intent to break it.

B) The vow is achieved, but not by me. I vow that I will chop down a given tree. When I get there, it has already been choppped down. 

9) The circumstances have been misrepresented to the person who makes the vow. A person makes an unbreakable vow, "If you get sick, I promise to take you to Dr. Bombay to get you better. You get sick. Do I take you to Bernard Fox? Do you die?

Bart