I don't think humans have spirits, though I know a few who are spirited. I suppose I believe in science, among other things, such as religion, which I'm pretty sure exists too. Anyway, I think the mind is a pretty supernatural thing without ascribing anything supernatural to it. In other words, I don't think admitting that it's the product of complex chemical reactions (cue grainy documentary) reduces it, or makes it any less mysterious and beautiful.
(I actually registered to try to help dispel the myth that all NFs are spiritual, religious, or both. Emoticon's for verification.)