The meat of the question stems from several things in HP lore:

  • people could get falsely accused and go to jail for nothing (Sirius Black for instance)
  • people could betray other people (Potters + Pettigrew + Fidelius charm)
  • people could say that they are not Death Eaters and were under influence of Imperius (Lucius Malfoy)

So, basically the vow of the following format could save both Ministry, Order of Phoenix (who whouldn't mind killing a Death Eater even if it would enforce stringent discipline in their ranks, eg taking the vow), Death Eaters (who actually used it casually (Snape-Malfoys)), bankers etc. from a world of headache:

Giver: "I swear to tell the truth regarding matter X and I swear not to conceal any facts that may pertain to the understanding and the appropriate line of questioning by Receiver"

Receiver: "I swear to hear the truth from the Giver and act accordingly and justly"

Binder: "I bind you bla-bla-bla"

Why wasn't it used as proposed? Maybe there is some rationale I'm missing.

  • 2
    A few quick ideas: 1) What if the person under interrogation refuses to take part? 2) Is it worth risking a juror/Ministry official to make every vow? (What if both people die if the Vow is broken? How do you judge “accordingly” and “justly” by the Vow’s standards?) 3) What if the person under question has a false impression of the truth?
    – alexwlchan
    Commented Dec 28, 2015 at 21:35
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    Because memory can be altered with trivial ease.
    – Valorum
    Commented Dec 28, 2015 at 21:50
  • 1) refusal to take part would be suspicious, wouldn't it? 2) only the giver is actually bound if I remember correctly 3) proper wording is actually a contest in loophole elimination 4) false impression of truth - would it actually trick the vow? It's a really powerful and dangerous instrument - maybe if there is or was truth in one's had it would be impossible to trick it? No idea.
    – pdeschain
    Commented Dec 28, 2015 at 21:51
  • 7
    @Vorren "Refusal to take part would be suspicious, wouldn't it?" is the same logic as "If you haven't done anything wrong you shouldn't care about intrusive government surveillance/overly loose stop and search laws/etc." Or, to put it another way, innocent people have as much reason to object as guilty people. If you're automatically viewed as a potential suspect because you don't want to participate in something that might kill you then the entire system is useless. Commented Dec 28, 2015 at 23:54
  • 1
    Read the Wheel of Time series with the Aes Sedai to learn the consequences of people being magically bound to tell the truth. Commented Jan 27, 2016 at 18:55

3 Answers 3


The Unbreakable Vow has very steep consequences, and is only as good as the wording of the contract. As a result, an unforseen consequence of the particular Vow could result in the accidental death of the Vow taker, or the Vow taker may end up being bound past the original purpose of the Vow, such that it's now a hindrance. To have a large number of people accidentally die, or trapped by the Vow seems like a huge burden. Signing a contract in real life can be a dangerous enough prospect without the consequence of death if you mess up.

And, on the other hand, poor wording could also leave loopholes that allows them to circumvent the intent of the Vow, making it pretty much useless. Or a fanatic (and it's known some of Voldemort's followers are fanatics) could intentionally break the Vow, knowing he will die, but thinking his cause is greater than his life, and the Vow gives him a great opportunity to look trustworthy, and get access to very important information. In other words, the Vow is not necessarily effective enough to justify the cost.

Most importantly, it would be basically be security through fear of death, which I would see as a type of totalitarianism. Widespread enforced use of the Unbreakable Vow would make them no better than Voldemort.

  • 1
    Not asking about being better than Voldemort, just purely utilitarian standpoint. But you make a decent point about vow's unintended consequences and potential for abuse.
    – pdeschain
    Commented Dec 30, 2015 at 8:40
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    I think the questionable ethics of asking someone to use it is a valid reason why it wasn't ever used.
    – Kai
    Commented Dec 30, 2015 at 16:41
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    ... That's just profoundly untrue. Yes, in real life there have been and will continue to be some unethical political decisions, but unethical political decisions are by no means guaranteed even if they are efficient.
    – Kai
    Commented Dec 30, 2015 at 17:40
  • 1
    Trying to say that universal sense of morality isn't inherent to human beings. It tends to differ from culture to culture. In hp world they live in war time, so drastic measures are possible.
    – pdeschain
    Commented Dec 30, 2015 at 22:48
  • 1
    Sure, such drastic measures are possible, but it's also possible (in fact, I'd say it's likely) that J.K. Rowling chose not to write this possibility because she did not picture the Ministry of Magic as being so unethical. If she had, the ending would have been very dark, Voldemort is gone, but the wizard government is still there being horrible. And that is the reason why I mentioned ethics in my answer.
    – Kai
    Commented Dec 30, 2015 at 23:15

The consequences are probably a bit too high for it to be used for everyday activities:

“Well, you can’t break an Unbreakable Vow…”

“I’d worked that much out for myself, funnily enough. What happens if you break it, then?”

You die,” said Ron simply.

Harry Potter and the Half-Blood Prince (Chapter 16)

  • 2
    Short and to the point! :) Commented Dec 29, 2015 at 1:45
  • 2
    I am not asking about every-day measure :) "high-security measure".
    – pdeschain
    Commented Dec 29, 2015 at 5:34
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    Think the case of Peter Pettigrew betraying Potters. The secret keeper should've been bound by vow.
    – pdeschain
    Commented Dec 29, 2015 at 5:41

I cannot fathom the amount of complexity and legal wrangling that would be required if the magical world turned to the Unbreakable Vow in order to ensure truthfulness.

Not only is the consequences quite steep for everyone from unlucky witnesses to defendants (death), how would the terms of the vow be construed? Every single person who provides testimony of any kind would need a team of lawyers in order to properly set the bounds of the vow. For instance, let's take the example you provide in your question. Here are a few things I'd be concerned about:

  • Under what conditions is the terms of the vow fulfilled? Currently, the vow looks like it will last an undetermined amount of time.
  • I'd like to think that witnesses and defendants have certain rights. How would the vow account for questions that potentially violate those rights in some way?
  • What happens if the prosecution or defendant representation has a sustained objection with a question asked? The vow probably doesn't really care and would expect a truthful answer.
  • Who, exactly is the receiver? The judge? The prosecutor? The defendants chief lawyer? Their associate lawyers?

Since I'm not a lawyer, there could be plenty of other issues, or even loopholes, that the vow would allow or ignore. Implementation of this vow would be incredibly complicated. However, there is a simpler solution, which I'm sure gets utilized on occasions: truth serum. However, since there are ways to resist the effects of truth serum, I assume legally, it would be treated like lie detector tests in real life.

  • 1
    If I remember correctly - the law system of magical Britain utilized not "rule of law", but "rule of men". The high court eg the Wizengamot basically could do anything to you And you didn't have a solicitor. So the question is of more practical nature, not about moral/judicial correctness/implications. Those guys have magic and they are not using it to the full extent even when the life of a man is at stake.
    – pdeschain
    Commented Dec 29, 2015 at 5:40
  • 3
    @Vorren: But the vow is quite specific and the consequences are absolute. Anyone who agrees to undergo this vow is opening themselves to any number of unknown scenarios for the rest of their lives, even if they beat whatever charges is being levied against them. And you also ensure that no witnesses will ever testify.
    – Ellesedil
    Commented Dec 29, 2015 at 5:55
  • 1
    Imperius seems like an alternative. Think about it - the concept of morality and lawfulness should and would be very different if such measures were possible.
    – pdeschain
    Commented Dec 29, 2015 at 5:57
  • 1
    Also, if it is possible to tamper with facts and recollections with trivial ease and law enforcement doesn't adapt - it's useless, because it basically does what is expected from it by any manipulator.
    – pdeschain
    Commented Dec 29, 2015 at 5:58
  • @mr.pd You seem to be conflating what Fudge and Umbridge tried to do to Harry (prevent him from defending himself, deny him his legal counsel, add arbitrary accusations mid-trial, dismiss witnesses and evidence without good reason, etc) with "normal" operations. In the book, the Wizengamot react quite negatively once they realise what's going on, and had probably been brought in under false pretences. Commented Aug 30, 2019 at 12:16

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