Modernism is a response to Romanticism. As more and more people become disillusioned with the state of the world before and during World War I, especially those artists and writers in self-imposed exile, modernism grows to encompass all creative human thought that places the power of the individual above all things. Since progress could not longer be considered "good" at any cost, many writers began to question the value of machines and industrialization. War and the Romantics became the enemy of humanism. It would eventually lead to Liberalism (not be confused with left-wing) in politics, evolution in science, Marxism, existentialism in literature, and progressivism in art (cubism, etc.)
James Joyce, Hemingway, T.S Eliot, Neitzche, Huxley, Camus, Modrian, and Picasso would become the most important voices of the modernist movement in literature and art.
In RPG terms, D&D could be considered the original modernist RPG, placing the character at the forefront of the story. GURPS and others could also remain modernist, with a slight deconstruction bent. Most games coming out as a response to D&D and it's hundreds of "improvements" would still remain modernist, because the structure of gaming does not change, even though the rules do.
Post-modernism is a response to modernism. Because modernism never fully realizes its goals, and because the rate of information accelerates, post-modernism begins to unravel the ideals of its predecessors. Postmodernity concentrates on the tensions of difference and similarity erupting from processes of globalization: the the accelerating circulation of people, the increasingly dense and frequent cross-cultural interactions, and the unavoidable intersections of local and global knowledge.
There are so many definitions of post-modernism, however, you'll never get two people to agree to what it truly is. Most story-telling that takes place in Entertainment today is post-modern, whether people like it or not.
My degree emphasis was in post-modernism and I'm still a little vague on everything it encompasses. Lichtenstein, Jackson Pollack, Dada, Jacques Derrida, Michel Foucault, Jean-Paul Sartre, Camus (again), and Franz Kafka would become important post-modernist and deconstructionists. Even Noam Chomsky is an important post-modernist.
In my opinion, most postmodern literature is just a "play" on the things that everyone is familiar with. There is very little creativity in post-modernism, but a great deal of sociopathy and nihilism (not to be confused with existentialism).
In RPG terms, most any INDIE game where the rules are striped down to the essentials of play and exposed to the reader would be considered post-modern.
Post-structuralism is probably a more appropriate term to associate to this new wave of design, however.
Certainly these movements have affected the "art of game design" which has historic routes, but very recent growth. Video games certainly entered the post-modern age much faster than RPGs ever did. Greg Costikyan has written an article about it
here . And I've talked about this briefly on my
site before.
Man. I can't believe you brought this up. Or that I responded with this much information at 3 in the morning.
Good start, I think. But I would love to read other people's feedback.