Ascending the spiral staircase and pushing open the door that straddled reality and illusion, one would arrive at the holy land coveted by scholars across the universe: the library of Nous, the Aeon of Erudition.
The seemingly ancient architecture was, in reality, a space in a dimension entirely separate from the outside world.
The shelves were filled with ancient-looking paper books.
But upon closer inspection, one would find torrents of light and shadow flowing within these books, like moving light cones.
The information density within any single book was no less than that of the interstellar library of an advanced civilization.
And such books were merely the most inconspicuous items in the entire collection.
If someone were to steal a few items from here, gaining even a fragment of this knowledge, they could, like the geniuses of the Genius Society, drive the development of the entire galactic civilization.
Of course, that was assuming they could actually understand the knowledge within these books.
After the Swarm Disaster, Nous stopped its calculations for the answer to the universe. Some believed this Aeon had given up, while others believed they had already unlocked the truth of the cosmos.
If the latter rumor were true, then this library must contain knowledge sufficient to explain the entire universe.
It wouldn't be an exaggeration to call it a collection of omniscient and omnipotent information.
Of course, Su Mo didn't think this was likely.
If Nous had truly explained the truth of the universe, truly solved the mystery of all things, and truly reached the realm of omniscience, then there would be no need for them to continue cultivating Emanators, no need to continue serving as an Aeon, and no need to meet with him.
Omniscience was not a realm so easily reached.
Moreover, the very idea that one could exhaust all truth through calculation alone was not necessarily sound.
With these thoughts, Su Mo and Holou surveyed their surroundings, ignoring one treasure trove of knowledge after another that could drive the entire universe mad. Finally, they stopped before an old man.
He was a blind old man with sunglasses and a cane, looking perfectly ordinary, like any other organic human life form.
However, Su Mo and Holou exchanged a glance, stopped in their tracks, and almost immediately understood the old man's identity.
Although they couldn't see any mechanical structures or detect any unusual aura, the only one who could appear here at this time was naturally Nous, the Aeon of the Path of Erudition.
"Every visitor who comes here asks their greatest question."
The seemingly blind old man keenly detected their arrival. He spoke slowly, his voice ancient and calm.
He was stating the rule of the library.
Whether they were a genius recognized by him or a guest who had embarked on the "Path of Enlightenment" to seek an audience, they were all entitled to ask Nous one question.
To this question, Nous would not give any answer.
He would only help them better explore the question, sometimes by reframing it, sometimes by granting them an auxiliary tool. Whatever the method, Nous's grace was a precious opportunity capable of opening the eyes of even the most ignorant.
Therefore, the journey to seek an audience with Nous was also known as the Path of Enlightenment.
In fact, this statement didn't need to be repeated.
Because only those who could articulate their question, who knew the greatest mystery they faced, could find the door of riddles and use the Key of Erudition to find this place.
Now, facing the arrival of Su Mo and Holou, Nous followed the same procedure as with all the other geniuses.
Su Mo had no objection to this.
He patted Holou's head, signaling for the young goddess to go first.
Holou paused, momentarily dazed. Su Mo had been the one to bring her in; she hadn't really thought about what to ask.
After exchanging a look with Su Mo, she didn't refuse.
Taking a half-step forward, the dazed-looking young goddess stared at the old man before her, tilted her head, and asked the most common yet never-before-asked question in this place.
"Who are you?"
The moment these words were spoken, the already quiet library became even quieter.
If anyone else were to witness this scene, their hearts would surely break with pain.
Even someone as proud as Herta would think Holou's question was a complete waste of an opportunity.
Are you kidding me? Even Herta had only had two chances to have an audience with an Aeon. For an opportunity that people across the universe would risk their lives for, you ask such a dumb question?
You're standing right in front of an Aeon, and you're asking who he is... Isn't that less dumb and more of a provocation?
Aren't you afraid Nous will just vaporize you?
Only Su Mo didn't find it strange. Since he had allowed Holou to ask the question, he was naturally mentally prepared for this outcome.
It must be emphasized that Su Mo's mental preparation was not about giving up this opportunity to ask a question. On the contrary, he had high expectations for Holou's question.
And in fact, Holou's performance did not disappoint.
Though she was quiet, she was as smart as they come. She had already learned most of the knowledge of this world from the Ex-Machina network. How could she not know who the person before her was?
But she still chose to ask this way, partly out of the innate curiosity of her Divine Core, and partly as a challenge to the being before her.
Su Mo rubbed Holou's small head in satisfaction, then looked at Nous.
"..."
Nous remained silent.
With his computational power, he could analyze the general situation of the two just from the various force fields they leaked.
But he truly could not answer Holou's question.
After a dozen or so seconds, Nous spoke to Holou.
"You are special."
Hearing this, Holou blinked, a trace of confusion in her eyes.
"And who am I?" she asked again, posing the ultimate philosophical question.
"..."
Nous fell silent again.
His silence was deafening.
How could an Aeon be questioned into silence by a little girl?
Yet, the scene before them was real.
If Herta and the others had seen this, after their initial surprise, they too would have immediately accepted the situation.
Aeons were highly condensed embodiments of philosophical concepts, but that didn't mean they had solved all philosophical problems.
In fact, only technology had advanced in the Honkai: Star Rail universe. In the field of philosophy, problems that existed during the Enlightenment era still remained unsolved.
Philosophy hatches theology, theology hatches science, and science attempts to solve everything with methodology, but so far, it has not succeeded.
Su Mo watched Nous with great interest, waiting for his reaction.
After a long silence, Nous spoke.
"I am the one who questions all answers. You are the one who questions all questions."
This statement was both an emphasis on their respective concepts and an answer to Holou's question.
Although this answer had the suspicion of being evasive, at this moment, Su Mo was more concerned about something else than nitpicking.
"Didn't you say you would only give questions, not answers?"
"Why this time did you directly give such a perfunctory answer?"
Faced with Su Mo's question, Nous answered with extreme calm.
"Because she is special."
Nous placed an unusual importance on Holou, whom Ruan Mei and Herta had largely ignored.
"Of course she's special."
Su Mo naturally understood Nous's meaning.
Otherwise, he wouldn't have specifically brought Holou to this world.
"As the one who doubts all questions, the skepticism this child represents precedes the epistemology you represent."
"So, I am very curious about one thing. Before you analyze all things and find the ultimate answer to the universe, have you ever truly confirmed that this answer actually exists?"
"Have you never once suspected that the universe itself is just an illusion, and your existence is merely a simulated character in a game?"
In just a few sentences, Su Mo had issued a dangerous inquiry, a question that even hinted at denying Nous's own Path.
If it were another, more hot-tempered Aeon, it wouldn't be impossible for them to attack Su Mo for this.
In a sense, Holou's Divine Core concept was the nemesis of Nous's Path concept.
As an Aeon, Nous's original purpose was to understand all things through logic and calculation, thereby uncovering the ultimate truth of the universe.
If he could succeed in this, successfully unraveling all the mysteries of the universe, Nous would be able to break through to the realm of omniscience and become an omniscient and omnipotent being.
For most scientists, Nous's existence was the greatest guide on the path of science. Even the development of the entire scientific community was almost built on Nous's theoretical foundation.
Almost everyone took it for granted that through logic, reason, and calculation, one could truly obtain the truth of the universe.
In fact, the prosperous development of the scientific community to this day has been a verification of this proposition.
However, under the prosperous development of epistemology and methodology, the shadow of skepticism has been growing in secret.
Even according to a purely logical analysis, before seeking the truth of the universe and understanding all things, one must first establish a premise: that the world is knowable, that the universe truly contains truth, and that reason can explain everything.
If this premise is taken a step further, it becomes the eternal philosophical problem mentioned before.
Cognition is a two-way street. If the world can be known, by whom is it known? If it is by me, then how can I confirm my own existence?
Nous was bent on solving the mystery of all things, on solving this equation called the problem of the universe.
And the doubt Holou represented came even before solving the problem. She questioned the problem itself.
Rather than solving the problem, she was more concerned with whether the universe existed, whether the self existed.
And this was the essence of the God of Doubt.
Hearing Su Mo's question, Nous did not get angry. He didn't have the emotion of anger to begin with. Answering all questions with logic and calculation was the essence of his Path.
Having a complete grasp of all the civilizational data in the entire universe, he was the one who could best understand the meaning of Su Mo's words.
So, he quickly gave his answer.
"The brain in a vat hypothesis cannot be disproven. For that very reason, it is meaningless."
The brain in a vat hypothesis refers to the idea that everything an individual perceives is a simulation of signals, that the world itself does not exist, but is just a dream of a brain soaking in a solution.
The brain immersed in the vat cannot awaken itself. Even if it suddenly awakens, no one can guarantee that this isn't a second layer of dreaming. Therefore, this hypothesis can never be disproven and can only be a topic of idle chatter.
The answer Nous gave was perfectly fitting, but Su Mo found it very interesting.
"Meaning? Isn't that something the Path of Elation concerns itself with?"
"Truth knows no Path."
Nous spoke calmly, then lowered his head, his blind eyes looking at Holou.
"Doubt is the shadow of nothingness. You once stepped into a fated slumber, but you did not truly walk towards IX... What changed you?"
This time, it was Nous who was asking Holou a question.