Why does the Department of Mysteries keep prophecies?

Question

What's the main reason why the Department of Mysteries keep prophecies?

The Keeper of the Hall is a Bureaucratic witch or wizard who orders and maintains the Records placed on the numerous shelves that comprise most of the Hall's interior. Presumably, after the Records are correctly assorted, stringent anti-theft spells are placed upon each and every one of them, allowing only those to whom the Prophecies refer the authority to remove them from their places. _{http://harrypotter.wikia.com/wiki/Prophecy_Record}

As far as I know, the Department of Mysteries is the department where they put recordings of prophecies, and that includes the prophecy about Voldemort and the one who's supposed to conquer his power. They are recorded and then put into those glass orbs.

Well, for this part, it seems reasonable that this is one of the most important prophecies since the Ministry of Magic wanted to find out how to conquer Voldemort's lust for power.

But I'm puzzled with this. Why do they even keep them? What significance do those prophecies have? There may also be certain items there that are very important or can play a great role for magic. But I can't remember why they keep these prophecies. Do they need them for future reference, fate guesswork, etc.?

Things to remember:

• The Department of Mysteries could have just stored the important prophecies. So there's a possibility that they stored those prophecies for an important reason or maybe a reference.

• I have a theory that they stored those prophecies for future references. There's a possibility that they will need it for a certain reason which I don't know.

Answer 1

Because they study mysterious stuff.

The Department of Mysteries is all about studying and unravelling the deepest and most inscrutable mysteries of magic and the universe. Prophecies count as mysterious, so they're all stored there, where the people working in that Department can study them at their leisure.

Why does the Department of Mysteries keep ...

• a locked room containing the essence of love?
• an archway with a veil containing the essence of death?
• an entire hall full of bottled prophecies?

It's all for the same reason: they study mysteries.

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As for your point that they could have just stored the important prophecies ... well, how do you know beforehand which ones are likely to be important? The whole point of prophecies is that they:

1. say something about the future, and
2. are often cryptic, their meaning hard to unravel.

Stuck here in the present, we can't know which statements about the future are likely to be important, even assuming we could understand those statements in the first place. OK, the one about Voldemort and Harry Potter was obviously significant, but that's an exception rather than a rule. Remember the butterfly effect: it's often impossible to tell beforehand which events are going to be significant and which aren't. Let's say there was a prophecy about the unrequited love of a poor boy from Spinner's End - who would have thought that that would end up having great significance in the history of the wizarding world? Or a prophecy about how Barty Crouch's son wouldn't take after his father ... or one about how a boy once thought to be a Squib would one day kill a snake. All of these are things which a priori might have appeared insignificant, but in hindsight turned out to be crucial.

Answer 2

On top of Rand al'Thor's answer, think about why a library (in the real world) keeps a copy of every book ever printed, and often a copy of every local or national newspaper, rather than just relevant or important ones.

As a reference, and in case it's needed.

Answer 3

This is actually bigger than, "They study Mysterious stuff", and while that is an acceptable answer, I don't think it is the whole answer.

Realize that these people are wizards, and while we are never shown exactly how far professional magic goes, we do know that the first magic you ever learn is how to levitate stuff. We also know that magic is actually difficult to learn. While never discussed exactly what it involves, there are multiple times where they have to learn theory behind transfiguration. So it's more than just wave your wand and chant some incantation. Magic is difficult, and yet first years are able to levitate giant wooden clubs. So, it would seem that magic has very broad scope.

Well, Ev, you're just rambling! No, I'm pointing out that wizards know a lot about the physical world. Even beginners can learn to turn gravity on it's head. The department of mysteries doesn't just study mysterious stuff, it studies the very few things that wizards haven't already conquered.

They can control:

• Light - lumos
• Sound - muffliato (made by a teenager)
• Gravity - levicorpus, wingardium leviosa, whatever enchantments are on brooms and flying carpets
• Space-time - apparition

basically all the stuff our physicists wish they could solve.

But they cannot control or understand:

• Death - they have a few life extenders, but no one knows what happens on the other side of the veil
• Time - they have invented time turners, but there is no indication that they can go forward in time, and there are very strict rules for when time turners can be used
• Love - Harry is somehow the first child ever saved by love
• Space - there is a mention of a space room in OOTP, presumably no one has ever gone to deep space successfully (though there is a claim that someone went on a ride to the moon on a comet 260 (i think), and while that claim is obviously false, it does seem that they would be able to make it to space by other means if by a broom is even slightly believable
• Prophecy - This is the part of time they don't understand the future. There are almost no actually seers and no one can tell the difference between frauds and real seers. Dumbledore explains that most of the prophecies in the hall of prophecy are not fulfilled, he also says that as a young man he dismissed the idea that any of it could be real at all. (He was unwilling to continue the subject at Hogwarts until he heard Trelawny give a real prophecy). So, how do you study prophecy? Keep a record of them all, and when they are fulfilled(?) take a look at them and who made them. Keep notes about the people, the way they did the seeing. (Did they use tea leaves? Proper prophecy? Crystal ball?).

The primary purpose of the department of mystery is R&D. They need to study things that are nearly unstudiable, so if it takes putting every prophecy ever in a big hall, that's what they'll do.