I was delighted by this - a chain letter whose information floats on the empty spaces of currency!
If you have not seen it, one of the Intellectual Wonders of the Internet is Daniel W. VanArsdale's paper "Chain Letter Evolution" (and the associated archive of paper chain letters), which establishes paper chain letters as evolving organisms whose information specifies their prospects for reproduction the way our genes specify our own. Copying chain letters by hand introduces the possibility for error, hence for variation - as with sexual reproduction and mutation in organisms.
Information that causes its environment to preserve and reproduce that information, survives and spreads.
Information on chain letters survives by motivating human beings to preserve and reproduce it.
Information in DNA survives by motivating organisms to preserve and reproduce themselves.
Pain, at its most functional and basic, is an attempt by genetic information to establish a relationship between a circumstance and an action. Pain from fire and pain from loneliness are both ways that information exploits us without regard for our well-being: genes that cause organisms to run from fire, or (in social organisms) seek social belonging, get propagated. Never mind the unlucky soul with third-degree burns covering his body in the ICU.
Viewed in this way, it is easier to see the relationship between pleasure and pain. Pain motivates an organism by causing it to do something different than what it's doing; pleasure motivates an organism by causing it to do more of what it's doing. Pain is something like negative feedback; pleasure is positive feedback. Given the need for moderation in the life cycle of a complex organism in a complex environment, and the inherent limitations of positive feedback, we might expect a priori for pain to dominate.
From "Chain Letter Evolution":
We have described the descent and variation of chain letters, and their differential replication depending on copied features present in the text. These processes assure that chain letters "evolve" - that is, they accumulate inheritable features that increase or sustain propagation. It is this evolution that ultimately explains "how chain letters work," and why they worked even as public attitudes and beliefs changed over generations. This success is even more remarkable considering the universal condemnation of chain letters from both secular and religious authorities, and the lack of any real service they provide to their hosts apart from dealing with the false hopes and empty threats that chain letters themselves created. [Emphasis mine.]
Why do we persist in propagating information that does us no good?
Why do we persist in propagating our own genomes when that information does us no good?