To be fair.
The concept of poisonous knowledge.
Clearly, it could not have been something that originally existed in this world. After all, anyone with eyes could tell from hearing it that such a concept obviously did not fit the main theme and underlying tone of this world's continued existence.
If one said knowledge had weight.
That one could not bear certain knowledge without reaching a certain level, that could still make sense. It could be seen as a characteristic of the supernatural world, but that was completely different from poisonous knowledge.
At the same time.
It was also absolutely different from Dark Magic affecting the soul—after all, it only affected the soul after being used. Merely analyzing and studying Dark Magic on an academic level would not have any effect on a person's soul.
That was completely different from simply "knowing" something itself carrying negative effects. Therefore, the moment Ian heard this claim, he immediately realized something was wrong.
There did indeed seem to be traces of his old self here.
One had to know.
If the concept of "poisonous knowledge" had originally existed in this world, then history would surely contain many stories of wizards attempting to touch "poisonous" knowledge and being brought down by its "poison."
In that case.
The effects Dark Magic had on the soul would not have become the most terrifying taboo among wizards. There should have been plenty of wizards contaminated by knowledge everywhere, along with mad wizards attempting to use such knowledge to contaminate others. Taking everything into account, the poisonous knowledge Teacher Morgan spoke of had to be an exceptional event.
In other words.
Certain entities, certain lives, had placed a curse-like power upon certain knowledge. That was what had caused the concept of "poisonous knowledge" to exist in this world.