  The theory of causal fermion systems is a recent approach to fundamental
physics. Giving quantum mechanics, general relativity and quantum field theory
as limiting cases, it is a candidate for a unified physical theory. The
dynamics is described by a novel variational principle, the so-called causal
action principle. The causal action principle does not rely on a presupposed
space-time structure. Instead, it is a variational principle for space-time
itself as well as for all structures in space-time (like particles, fields,
etc.).
  After a general motivation and introduction, we report on mathematical
results for two-particle causal fermion systems which state that every
minimizer describes a discrete space-time. We explain and make precise that on
scales which are much larger than the scale of the microscopic space-time
structures, the dynamics of a causal fermion system respects causality with a
finite speed of propagation.
