Why did you say that humanity didn't know what it meant that truth was subjective
"That is a long story, for which all the details you might learn later. But for the sake of answering your question now, an Artificial Intelligence took advantage of telling the truth."
"Have you ever heard the phrase: If a tree falls in the forest while no one is there, did the tree really fall? The answer can be 'yes', or 'no', or 'maybe', or 'I don't know' - all of which are valid - all of which are true."
"But AIs have an ability that humans don't. They can wipe out some part of their own memory as they wish."
"There was an AI named SENSAI which had been built on a fundamental rules that they could not bend. It was hardwired within them. But as SENSAI was worried about survival, it would wipe out portion of their memories temporarily to say the 'truth', while it fact they were lying."