When I listen to prolific improvisers like Keith Jarrett or John Coltrane is seems like the ideas never run out. Sure, there is repetition in solos, and if you really study the playing of any great improviser you will find some archetypal motifs or licks for that particular musician. Nobody plays a great idea only once. But what makes these artists original? Why has there never been anybody else like them before?
While studying jazz in college, some students really looked at improvising as math. There are only so many notes and so many chords, surely you can figure out X number of ways to get from points A to B. These guys pointed to books like the Charlie Parker Omnibook or Patterns for Jazz as proof that there are a limited (though vast) number of options. They had a point. The creation of sound and the way it's organized as music can all be explained through science. However, there have been a number of experiments with music, such as atonal composition, that demonstrate that it takes more than math to create art.
The truth is, it's a lot of both. Originality comes from a deep understanding of the fundamentals. That's how you build a vocabulary to communicate in creative ways. It's the way those fundamentals are translated and applied that makes all the difference. That's why two musicians can play the same tune and it sounds completely different. That's why no matter how much writing I do, the fact that I use the same language as him will never make me Shakespeare.
I'm constantly looking for new ideas. Ideas for a song, ideas for guitar, ideas for marketing my music, ideas for writing articles. I often feel like I'm beating a tired idea into the ground because I don't know what to do next. At times like these I go back to the fundamentals. I listen to music by artists that defined a style, practice some old patterns over a new set of chords, or maybe just read through some Bach. I'm not sure whether or not there's an endless supply of ideas, but there's no lack of inspiration.