Postmodernism is like a bar of soap in dirty bath water, as soon as you think you have a good grasp it slips out of your hand and is lost in the murky water leaving you groping again blindly.
Perhaps it is hard to get a hold of because it isn't really born out of a linear, cognitive thought process-that would be too modern. It is really more of an emotional reaction to modernism than a philosophical choice. I find it almost a little humorous to read how people analyze postmodernism from the viewpoint of a linear philosophical process as though it was all thought out in advance and we all agree on a chosen philosophy of life. Postmodernism is not a logical choice as much as an emotional and even cultural reaction.
There really shouldn't be a postmodern manifesto as though someone sat down and wrote out what our thoughts are and where we are heading. As soon as someone does it will be offensive to the rest of us, after all, we're postmodern and angry at the world! You can't put a label on us!
Even the name "postmodern" lacks logic. How can we be post-what is now? Does that make us futurists? However, the word really is fitting in many facets because postmodernism is really just a reaction against something. It is looking at the modern experiment and declaring it a failure. It is more about what it isn't than what it is. Defined by what it is against rather than for.
Modernism, born in the enlightenment, lied to us. It told us that the human mind could solve all our problems. President Lyndon B. Johnson declared that poverty would be done away with in our generation. Johnson is gone, poverty remains. Science promised we could eliminate all disease like they did with small pox. Today we have more disease than ever, new diseases are running rampant--and small pox is threatening a comeback. Modernism has failed. Welcome to a world of postmodernism.