When the Who played on the Isle of Wight in 1970, they opened (at two o'clock in the morning) with a song called "Heaven and Hell."  It is a paean to judgment, hope, and immortality.  After describing heaven as a place where "you go if you've done nothing wrong" and hell as a place in the ground where "you grow horns and a tail and you carry a fork, and moan and wail," it goes on to wish, "Why can't we have eternal life, and never die?"
     Ah . . . as Nietzsche might have said, "human, all too human!"  What is about us, we human beings, we frail and fumbling bundles of muscle and bone that makes us long to live beyond this life, to live beyond what we will ever live in this reality?  Why do we wish so strongly to extend our lifespan?
     One obvious answer is that, from our vantage point on this planet, we do not see anything else.  We do not see anything beyond this present existence.  How could we?  We're finite.
     Another, perhaps less obvious answer is that somehow, some way we are looking for something, something that we sense we should have, something that, given who we are, we believe we should know.  We think in immaterial terms, we dream in eternal frameworks; why should we not experience such things firsthand?  Why should we not step into an experience our mind and heart seem to know, perhaps for no definable reason, should be?
     Though we can dismiss such longings as natural fears about material immortality, we cannot dismiss the reality that we dream them.  We cannot dismiss that we think about existences beyond our present one.  No one can honestly say that he or she has never, absolutely never done so.  No one.
     Chemicals do not explain everything.