>>13664488String theory is the theory of gravity which starts out by postulating that only things at the boundary of space-time make sense. The local space and time have to be reconstructed from the boundary description. This is called the holographic principle. In the 1960s, a primitive vesion of this idea was called the S-matrix principle.
There are two kinds of boundaries, those far away from everything, called "cosmological" and those which are on top of matter, called "black hole horizons". The description of these two horizons are similar. The oscillations of these boundaries describe the entire space-time nearby.
The detailed form of string theory begins with the postulate that there are black holes that make extended, light, 1 dimensional lines. The vibrations of these black holes then must account for all the particles in the theory, because the vibrations of a black hole encodes anything that can fall through.
