@scratchme1010: I have a little coffee table book called "Spooky Science" that debunks spiritualism thoroughly enough. "The Magic of Reality" by Dawkins makes a good case against it, too: Why believe in supernatural things that would require a rewrite of all the laws of physics to accommodate them? Why take the more complicated route? If you have a proponent who wants you to believe in ghosts or gods or whatever, why believe when you could just question his/her motives?
And I simply ask the question: What is a spirit? No hand wavery, just what is it? My friend suggested that it's "the opposite of flesh", which is... what exactly? I do offer a definition, too, and it's simple: It's a ploy. :)
I have learned that religious and spiritualist ideas evolved right along with mankind, out of Africa, with kings long forgotten being deified into gods that we still know today, like Osiris. That also goes for divination practices, like the Odu Ifa in Yoruba religion and the I Ching, both of which are mathematically based and rather fascinating in that regard. Actually, it is truly fascinating that math, even very advanced math, grew up out of divination. This, to me, says that these were just ancient people using their heads and trying to understand the world around them, not that they were 100% correct about everything.
If you can explain something and where it comes from, it really takes the edge off of it.