Okay.
The main problem with such evidence is that virtually all of it is anecdotal. There's very little quality control on personal testimony (the reason scientists discount it when conducting double-blind studies), so it can only ever be suggestive, not definitive. It can be collected in ways that skew the testimony, it can pass through multiple paraphrases (the "telephone effect"), and years can pass before such testimony is recorded, increasing the chances of hanky-panky even <i>without</i> intentional fraud. So, we should be automatically cautious. Be that as it may, there <i>are</i> ways of determining whether actual, bona-fide paranormal events occur, they just need to be studied in clever ways, and sensationalistic claims need to be critically analyzed.
Near-death experiences often contain seemingly hallucinogenic elements, like unicorns or talking flowers. They vary by culture, with Christians (obviously) seeing Jesus, while Muslims and Hindus encounter their own, unique religious imagery. In the same vein as the hallucinogenic stuff, people have encountered <i>living relatives</i> there, or experienced things that didn't occur in reality (i.e., seen doctors perform a procedure that actually wasn't). A lot of their often-reported features, like the blinding tunnel of light, have been reproduced with drugs like Ketamine.
The above doesn't say, of course, whether any particular NDE is legitimate. It just tells you that clearly, there is strong reason to believe <i>at least some NDEs are physiological.</i> That, in turn, very severely undermines the claim that they're evidence of an afterlife.
Two further, negative facts need to be mentioned: <b>(1)</b> people sometimes claim that, after an NDE, they acquire psychic powers (or are actually given visions of future events within the experience itself). They're not, however, any more successful than other psychics (that is to say, not at all). <b>(2)</b> Studies have been conducted with random words, and the like, attached to the top of a bookcase or other piece of tall furniture in an operating room or hospital bed, in such a way that a patient couldn't see them, but a spirit floating above the bed (during an out-of-body experience) could. None of these have confirmed that eerie, claimed capability to float outside the body.
Keith Augustine's <a target=new class=ftalternatingbarlinklarge href="http://www.infidels.org/library/modern/keith_augustine/HNDEs.html">Hallucinatory Near-Death Experiences</a> and the <a target=new class=ftalternatingbarlinklarge href="http://skepdic.com/nde.html">Skeptic's Dictionary entry</a> are some very thorough rundowns of the available evidence. In turn, they reference the primary literature, if you want to go wading through journals like the <i>Lancet</i> or <i>Death Studies</i>.
We should be wary of taking anecdotes, even when they appear convincing by themselves, at face value. This is because, taken in isolation, it's very easy to forget (to name but one example) the 50,000 times someone thinks of a long-lost friend, <i>without</i> them calling immediately afterward. But the one time it does happen is sure eerie! Similarly, lots of people have "prophetic dreams" (I, myself, just had one involving a terrorist bombing that would have occured today in New York--it didn't, of course). But the few times they do match up, by sheer coincidence, can be taken as stunning confirmation of something miraculous. That's why we don't just look at whether prophets get stuff right, any amount of the time, but whether they get stuff right <i>statistically more often than you'd expect by chance</i>.
Similar principles apply to almost any claimed encounter with the paranormal. If you dream about a relative unexpectedly, and find out the next day they're alive and well, you forget about it. If you dream about them, and find out they just died the previous night, it's downright creepy. Did their spirit visit you? Certainly, the temptation is there--an often overwhelming one--to believe that, as it would imply you'd get to see them again... but is it true? When you think about it some more, it doesn't necessarily mean they visited you, just that, in a world of 6 billion people, the weirdest coincidences can naturally happen. And since there's such a huge variety of <i>potential</i> coincidences, it's guaranteed that at least a couple will happen to you, personally.
That's not to demean or lessen any particular experience you interpret as spiritual, but ask yourself this: If something could happen <i>without</i> there being a spirit world, how can it be evidence for the spirit world? :\
So, what little rigorously methodic research there has been on NDEs has been disappointing, once taken in context. They contain features which strongly suggest a physiological origin. And you have very powerful, well-studied evidence from neuroscience making the existence of souls appear implausible, on the face of it (the mind-brain unity which I noted above). I'd say that, barring some future discovery that somehow turns everything upside down, there's not much room for a soul here...
The main problem with such evidence is that virtually all of it is anecdotal. There's very little quality control on personal testimony (the reason scientists discount it when conducting double-blind studies), so it can only ever be suggestive, not definitive. It can be collected in ways that skew the testimony, it can pass through multiple paraphrases (the "telephone effect"), and years can pass before such testimony is recorded, increasing the chances of hanky-panky even <i>without</i> intentional fraud. So, we should be automatically cautious. Be that as it may, there <i>are</i> ways of determining whether actual, bona-fide paranormal events occur, they just need to be studied in clever ways, and sensationalistic claims need to be critically analyzed.
Near-death experiences often contain seemingly hallucinogenic elements, like unicorns or talking flowers. They vary by culture, with Christians (obviously) seeing Jesus, while Muslims and Hindus encounter their own, unique religious imagery. In the same vein as the hallucinogenic stuff, people have encountered <i>living relatives</i> there, or experienced things that didn't occur in reality (i.e., seen doctors perform a procedure that actually wasn't). A lot of their often-reported features, like the blinding tunnel of light, have been reproduced with drugs like Ketamine.
The above doesn't say, of course, whether any particular NDE is legitimate. It just tells you that clearly, there is strong reason to believe <i>at least some NDEs are physiological.</i> That, in turn, very severely undermines the claim that they're evidence of an afterlife.
Two further, negative facts need to be mentioned: <b>(1)</b> people sometimes claim that, after an NDE, they acquire psychic powers (or are actually given visions of future events within the experience itself). They're not, however, any more successful than other psychics (that is to say, not at all). <b>(2)</b> Studies have been conducted with random words, and the like, attached to the top of a bookcase or other piece of tall furniture in an operating room or hospital bed, in such a way that a patient couldn't see them, but a spirit floating above the bed (during an out-of-body experience) could. None of these have confirmed that eerie, claimed capability to float outside the body.
Keith Augustine's <a target=new class=ftalternatingbarlinklarge href="http://www.infidels.org/library/modern/keith_augustine/HNDEs.html">Hallucinatory Near-Death Experiences</a> and the <a target=new class=ftalternatingbarlinklarge href="http://skepdic.com/nde.html">Skeptic's Dictionary entry</a> are some very thorough rundowns of the available evidence. In turn, they reference the primary literature, if you want to go wading through journals like the <i>Lancet</i> or <i>Death Studies</i>.
We should be wary of taking anecdotes, even when they appear convincing by themselves, at face value. This is because, taken in isolation, it's very easy to forget (to name but one example) the 50,000 times someone thinks of a long-lost friend, <i>without</i> them calling immediately afterward. But the one time it does happen is sure eerie! Similarly, lots of people have "prophetic dreams" (I, myself, just had one involving a terrorist bombing that would have occured today in New York--it didn't, of course). But the few times they do match up, by sheer coincidence, can be taken as stunning confirmation of something miraculous. That's why we don't just look at whether prophets get stuff right, any amount of the time, but whether they get stuff right <i>statistically more often than you'd expect by chance</i>.
Similar principles apply to almost any claimed encounter with the paranormal. If you dream about a relative unexpectedly, and find out the next day they're alive and well, you forget about it. If you dream about them, and find out they just died the previous night, it's downright creepy. Did their spirit visit you? Certainly, the temptation is there--an often overwhelming one--to believe that, as it would imply you'd get to see them again... but is it true? When you think about it some more, it doesn't necessarily mean they visited you, just that, in a world of 6 billion people, the weirdest coincidences can naturally happen. And since there's such a huge variety of <i>potential</i> coincidences, it's guaranteed that at least a couple will happen to you, personally.
That's not to demean or lessen any particular experience you interpret as spiritual, but ask yourself this: If something could happen <i>without</i> there being a spirit world, how can it be evidence for the spirit world? :\
So, what little rigorously methodic research there has been on NDEs has been disappointing, once taken in context. They contain features which strongly suggest a physiological origin. And you have very powerful, well-studied evidence from neuroscience making the existence of souls appear implausible, on the face of it (the mind-brain unity which I noted above). I'd say that, barring some future discovery that somehow turns everything upside down, there's not much room for a soul here...