  The Standard Model of particle physics was established based on the
equivalence principle and gauge invariance. The Lagrangians were built upon
experimental data demonstrating the violation of discrete symmetries together
with ideas of spontaneous symmetry breaking. The features of vector and
axial-vector interactions and chirality principle are manually added on in
order to fit in the observation data, rather than explained by the model as one
may hope. Here we develop a theory of interactions based on the Dirac algebra
together with the exterior operations the wedge product and the star operator
on the space-time, and develop a scheme for determining all possible
interaction formulations. In our scheme, the chirality transformation and the
left and right handedness come up naturally. A simple postulate about the
universality of physical interactions based on the space-time causal structure
yields the attracting features mentioned above as consequences.
