Why did the chambers in Philosophers Stone let people pass?

Question

More specifically Severus's chamber. One part of his riddle read:

One among us seven will let you move ahead,

If the whole point of guarding something, is so someone couldn't get it, why let or give someone the chance to advance, to get the object? It doesn't make sense does it? Why give someone the chance to get the object?

You may say, "So that the teachers (or Dumbledore) can retrieve it when needed."

However if the teachers made the chambers, they would create it in such a way, that only them (or any other selected people) could get past it.

OR

They would create it in such a way, that they could "hack" it, and pass the information to selected people.

Other chambers include Filius's, and Minerva's. (The flying keys, and the chessboard) These both give someone the chance to let someone pass.

Answer 1

I think Dumbledore may have committed the same arrogant mistake as the Dark Lord did. Recall chapter 26 of Harry Potter and the Half-Blood Prince.

‘Yes, I think so: only by drinking it can I empty the basin and see what lies in its depths.’

‘But what if – what if it kills you?’

‘Oh, I doubt that it would work like that,’ said Dumbledore easily. ‘Lord Voldemort would not want to kill the person who reached this island.’

Harry couldn't believe it. Was this more of Dumbledore's insane determination to see good in everyone?

‘Sir,’ said Harry, trying to keep his voice reasonable, ‘sir, this is Voldemort we're –’

‘I'm sorry, Harry; I should have said, he would not want immediately to kill the person who reached this island,’ Dumbledore corrected himself. ‘He would want to keep them alive long enough to find out how they managed to penetrate so far through his defences and, most importantly of all, why they were so intent upon emptying the basin. Do not forget that Lord Voldemort believes that he alone knows about his Horcruxes.’

Professor Dumbledore wanted to use the Philosopher's Stone as a lure for a clever trap, so that he can find out more about who is determined enough to go through all the traps. The chamber did indeed work for this purpose: he has uncovered Professor Quirrell as and agent of the Dark Lord that way, and has learnt more about Harry and his friends.

Answer 2

Unfortunately, I can't give any hard proof to back up this answer:

By creating challenges, rather than merely impassable wards, the teacher's traps served to:

• Keep students from investigating
• Weed out lesser wizards that may have heard about the Stone
• Slow down better, more determined wizards, in order to give Dumbledore time to act

In particular, Dumbledore suspected that only Voldemort would be needful enough of the Stone to venture into Hogwarts and pass the challenges. The challenges were made to be riddles/things to be overcome, because Voldemort's ego would force him to complete the challenges, as opposed to blowing them up/bypassing them with force. Since Voldemort "knew" the challenges had answers or solutions, his belief that he was smart enough to solve them would keep him occupied.

Any other methods, such as protective shields, would only have worked as long it took for Quirrell/Voldemort to figure out how to bring them down. Then, once that bit of magic was discovered, Quirrell would bring the shields down and immediately have the Stone.

I do not believe it was Dumbledore's intent that Harry, Ron, and Hermione enter into the trials to retrieve the Stone, as the currently selected answer supposes. Dumbledore was not so irresponsible to have First Years face off against someone he suspected to be working as an agent of Voldemort, or a form of Voldemort himself.

The enchantment on the Mirror of Erised was not targeted to Harry or his friends. It was for anyone who wanted the Stone, but did not want it for themselves. Dumbledore himself would have qualified for this. So, the final Mirror protection was more to key the Stone to Dumbledore or one of Dumbledore's trusted agents, and not so that children could access it.

I believe my theory Dumbledore's plan for the challenges to slow down the thief is implicitly proven with the fact that Dumbledore did indeed return to Hogwarts (from London) in time to prevent Quirrell/Voldemort from getting the Stone, even though Harry had been rendered unconscious.

Answer 3

It was Dumbledore that had planned it this way.

He is the one that asked specific teachers to put their own "trap" in each of the chambers. He chose the teachers in this specific way because he knew that Harry, Hermione and Ron all together could break the spells and traps of all the rooms.

And the last "trap" or spell and nonetheless, The Dumbledore spell to be able to obtain the stone.

"It was one of my more brilliant ideas, and between you and me, that's saying something. You see, only one who wanted to find the Stone--find it, but not use it--would be able to get it, otherwise they'd just see themselves making gold or drinking Elixir of Life. My brain surprises even me sometimes..." -- Albus Dumbledore

The chambers would let people pass but not just anyone, so he knew that all of these traps could be unlocked by the cooperation of Harry and his two friends, even before they've met each other.

So if someone other than these three students were to pass, at the end, no one but Harry could get their hands on the Philosopher's stone.

Answer 4

If they wanted the stone completely inaccessible, the only real way would be to bury it. Maybe not even then.

Presumably the stone would have needed to go back to Nicolas Flamel at some point so that he could continue to use it. So each of the teachers putting protections on it would have been needed to access it, just like many keys with many locks. This unfortunately doesn't prevent those locks from being brute forced, or bypassed, just like Gringotts was.