Stumbled over this interesting question and viewpoint on the PC Forum Eventspace - Great Weird Ideas section:
The alchemy of the 20th century
Neal Stephenson was asked: "What's the alchemy of the 21st century."
The context of this question was a discussion of Newton and his fascination with and attempt to "rescue" alchemy. Stephenson explained this fascination as part of Newton's attempt to reconcile his belief in God with his attempt to explain the physical world in mechanistic terms.
Upon hearing this, Dyson asked "What's the alchemy of the 21st century?" to which Stephenson answered roughly (I cannot recall precisely): "Attempts to explain consciousness, free will, the soul, etc." The 21st century is still entirely ahead of us, but I suspect Stephenson might be right: the 21st century is likely to see much unification among biology, chemistry, and physics, but it's likely that consciousness in general -- and free will in particular -- will continue to confound all three sciences.
Looking backwards, however, it seems to me that the alchemy of the 20th century is quantum mechanics. This is not a comment on quantum mechanics as a theory of physics, which explains much in the physical world and even has had utility in engineering. However, QM has been imbued with religious and mystical interpretations that go well beyond the theory itself. In these meta-physical interpretations, QM has become for many 20th century scientists what alchemy apparently was for Netwon.
An irony: Newton was so concerned about the compatibility between God and a Newtonian universe that he felt obliged to "rescue" alchemy. Although he didn't succeed with alchemy, his larger goal was achieved: Just past the start of the 20th century, when QM was first being hatched, physicists had become so comfortable with the compatibility between God and a (relativistically) Newtonian universe that Einstein discounted QM with his now famous remark, "God does not play dice with the universe."
-- Raymie Stata