No reason justifies disbelief.

[LadyForCamus]

Yes, it's complicated.  However, I think Belaqua has attempted to describe another way of collecting knowledge, and it was summarily discarded.

My view of things is this: we start with raw experience, filter it through our world view, and then categorize and systematize it.  There are plenty of experiences, in my opinion, which are so intellectually, emotionally or philosophically powerful that they are worth categorizing as such.  You might call them religious experiences, or moments of realization.

I myself have had experiences which I recognize as matching descriptions of religious experience.  I can honestly say to a Christian talking about the feeling of communion with God that I've been there.  Personally, I don't think it's necessary to attribute the experience to God or any other mythological source.  But what I CAN say is that the truth of that moment is self-contained: either you've had the experience and can "get it," and can understand why Christians might call it God, or you haven't had that experience.

This is an interesting thing you've mentioned here.  I have had This Experience while listening to a particular piece of music, in particular moments in time. It was a 100% unique, and as you called it, self-contained experience, in that if the music had been seconds on in the piece; if I had heard it a minute later than I had; if my brain chemistry had been even a shade different than it was at that  exact moment, I wouldn't have had the experience. I even did attribute it to god once, when I was young. Then I began treatment for depression/anxiety.  I started medication.  My emotions are far more even-keeled now; I don't have the horrid mood swings anymore, but I don't have Those Experiences anymore either. I understand why Christians call it god, but it isn't god. It's just a brain, doing things.

Science might provide interesting insights.  Very many so-called spiritual experiences have been reproduced in the lab: lucid dreams, OBEs, near-death experiences, and so on.  But in my opinion, having the experience provides a level of insight that none of the mechanisms a scientist might use can proxy for.

But, just because science can't recreate the experience, doesn't mean that there is some woo-element to what it is, or what caused it.

There's another path by which experiences can be confirmed: by the following of instructions meant to arrive at a particular mental realization or state of mind.  The problem is that it often requires an investment that an unconvinced party is unwilling to make-- and those unwilling to make it, being unable to reproduce the experience, will nevertheless place the BOP on those who outlined the path to having the experience, and discard both the experience and verbal descriptions of the kind of realized truth the experiencer had.

A simple example would be that of lucid dreaming.  If I told you that you could wake up in your dreams, and have complete control over the dream content, and that in this state, the dream felt much more vivid and full of detail even than waking life, then what next?  You could discard my assertion as woo or as an overzealous exaggeration.  But I have actual knowledge of lucid dreaming that your appeals for me to "show the evidence" cannot devalue.  To really be qualified to discuss the issue, you'd have to have a lucid dream, the steps of which can fairly easily be followed by all.

Well, lucid dreaming is fairly well understood from a scientific standpoint, if I remember correctly. I have lucid dreams all the time.  In fact, I suffer from hypnogogic/hypnopompic hallucinations rather frequently. Science also has a grasp on the cause of those experiences. Just because someone doesn't have first hand experience of something, doesn't mean they don't know something about it. If we can identify a cause, and we can identify an effect, what's left that matters?  If I only had the experience of these hallucinations without any knowledge of what they actually are, and what causes them...well, that could leave me open to any number of terrifying possible thoughts, wouldn't it?  Maybe I would think I was possessed, or being haunted, and then commit suicide. Conscious experience is an effect. I can't think of any reason to give it its own special category.

So the short answer to your question: another way of arriving at knowledge is by personal introspection.  And the categories of truth arrived at in this way are qualitatively different than those arrived at inference from objective observation.

How do you know exactly what you have knowledge of? How do you know it truly is what you think it is?