  This is a theory for the fundamental structure of nature based on spinors as
unique building blocks. Confinement of the spinors in particles is due uniquely
to the dynamics of the collisions between them. The interaction operator
contains only spin and momentum operators. The eigenfunctions of the
interaction operator have negative as well as positive eigenvalues, limited in
magnitude to the Planck energy. Interactions in one-center particles between
spinors with eigenvalues of different sign tend to bring the energy of the
particle closer to zero.
  At the origin of the energy reduction through interaction is the spin
precession, taking place when two spinors of different type come together. The
model can explain the existence of stable particles and all the known forces,
including gravitation.
