: I was thinking, and came up with this: No one has an original thought
: anymore.
Yes, but many important thoughts are formed by the combination of different ideas; Darwin's theory of evolution came about in part because of Charles Lyell's book Principles of Geology, which in turn drew from James Hutton's work in the field of geology, which could not have existed without Bacon's development of the scientific method... Isaac Newton perhaps put it best: "If I have seen further, it is by standing on the shoulders of giants."
It is inevitable that any concept or work will draw ideas and inspiration from preceding works, but that does not indicate stagnation. To use Marathon as an example: The basic ideas (spaceships, colonies, AIs, cyborgs) have been used thousands of times before in books, movies, games, etc., but the way Marathon combines these elements makes it unique from any of these works. Also, Marathon has another level beyond the basic storytelling; enigmatic characters and events, along with some interesting philosophical questions, give the player something to consider outside of the game.
Ideas are like language. It doesn't really matter that there are only twenty-six characters in the English alphabet; these letters are more than capable of expressing virtually every concept, often in multiple ways. Likewise, it is possible to sequence and combine basic ideas to arrive at a higher idea, as Nietzche and Spencer did with Darwin's theories. Another good example of this is DNA; out of the same four nucleotides, every individual organism on earth can be defined as a unique genetic code.
It doesn't matter that there aren't any new ideas; just as long as there are new combinations of ideas everything should continue to go well. And when we run out of possible combinations, odds are we'll have forgotten half of them and can just recycle those.
