Context: this is a follow-up to my last question Is the hallucination hypothesis always the best explanation?
Suppose A has a subjective experience (or multiple subjective experiences) that leads them to believe in the existence of X (they claim to have observed/experienced X). There are two extreme cases:
Case 1: if A is the only person on the planet who claims to have subjectively experienced X, then the hypothesis that A hallucinated X is considered highly plausible.
Case 2: if X is reported to have been experienced by all or most people on the planet, we normally say that X is a mundane experience, or in other words, that there is a high intersubjective agreement about the existence of X, and therefore the hallucination hypothesis is typically considered highly unplausible.
But what about cases situated between these two extremes?
For example, imagine that there is a very peculiar experience that only 0.1% of the world population has access to under very specific conditions/circumstances. People who have this experience typically conclude that Y exists, with very high intersubjective agreement (within this privileged group), although the remaining 99.9% of the world population would disagree, since they have never experienced Y (we could say that they are Y-blind).
I'm using 0.1% as an example, but more generally, what is the minimum threshold of intersubjective agreement (1%, 10%, 50%, 99%) that would make belief in Y justified (from the point of view of the people who (claim to have) experienced Y)? Does the amount of required intersubjective agreement depend on (the nature of) Y, and if so, how?
Is it possible to be justified in trusting one's subjective experiences even if no-one else claims to have experienced the same? I'm thinking of hypothetical situations such as a person being abducted by benevolent aliens who take them on a tour around the galaxy and then bring them back to the Earth, without producing any sort of physical evidence that this person could provide to convince others. In this case, the intersubjective agreement would be 0%, and yet would this person be justified in their belief that the things they experienced were real? We can extend this thought experiment to people who claim to have personally experienced ghosts, demons, angels, deities, God, astral projection, nonduality, psychic abilities, witchcraft, mystical experiences, miracles, paranormal stuff, etc. By the way, this question probably overlaps with Can I know something but not be able to justify it to anyone else?
EDIT: Someone in the comments objected to my 0.1%/99.9% hypothetical example with the following counterexample: Give us some credit! Only 0.008% of the world population experience tritanopia, yet there is no serious doubt among the 99.992% of us who don't experience it that it exists. Very good point. I concede the critique. The remaining 99.9% might in fact agree, disagree or withhold judgement depending on the epistemological standards of each individual, so the blanket assertion "everyone else would disagree" would not hold true in many cases. However, if the experience Y being reported by the minority group is quite extraordinary and worldview challenging, the rest of the people are more likely to react with skepticism and explain away the experience with different hypotheses (e.g. "they are lying", "they hallucinated", "they were deceived by an illusion", "they are crazy", "they are misinterpreting their experiences", "they are exaggerating", etc.)