  This work starts with the observation of a certain "rule" (up to now
unexplored) in the fundamental laws of Nature. We show some evidence of this,
and formulate it as a fundamental principle which exhibits a number physical
consequences. In particular, a new, very simple and extremely aesthetic unified
model, which includes supersymmetry and supergravity, naturally arises from
this principle, together with some new "physics". Furthermore, the new
interpretation of Kaluza-Klein extra dimensions we advocate here provides a
natural argument for dimensional reduction, and the agreement with the observed
phenomenology is recovered. In the high energy regime, a new physics is
expected. Consequences in QFT are shortly commented. Finally, we observe a
structure of "levels" and formulate a general conjecture about such a concept.
