Reincarnation? Heck no. Deja vu seems to me to simply be a weird mental screw-up. Happens to me all the time, never thought much about it. Odds are, something similar had happened before, and something (topic of conversation, setting, etc.) matched perfectly with the past event, and it triggered some sort of memory glitch, which gives the brain the impression that it happened before. If I devote a lot of thought to it (I usually don't), I can typically remember a similar event.
Don't get me wrong - I'm a strong Christian, I believe in a spiritual side to things, particularly when it comes to demonic involvement in "ghost" sightings - but if there's a probable natural explanation, that's what I typically go with. Which leads me to believe that past life "experiences" are simply mental events triggered by things we've read/seen/heard/done in the past. It simply strikes me as far more logical and probable, alongside the fact that it completely goes against the Bible.
ON, when it comes to "presences," I'd be careful. I know you're not a Christian, but I'll throw out this warning anyway for the benefit of Christians or Jews with similar experiences - there's very likely spiritual deception going on there. I don't just dismiss ghost sightings, in fact I take them VERY seriously. Satan is a very clever fiend, and his legions have had all of human history to learn to play off of our fears and/or desires. I have a couple of Christian friends who have literally seen "ghosts," and these men are serious about their faith.
Stepping off the soapbox now.
(Sorry if this in any way leads to a thread hijack, but that last paragraph seemed necessary.
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