  preserves parity; it applies to all massive spin \(\bfrac{1}{2}\) particles (fermions) and all massive fermions are known to obey parity conservation. However, a single Weyl spinor, either \(\psi_{L}\) or \(\psi_{R}\), does not preserve parity. Weyl noted that instead of the four-component Dirac spinor “two components suffice if the requirement of left-right symmetry (parity) is dropped”. A little later he added, “the restriction 2 removes the equivalence of left and right.  It is only the fact that left-right symmetry actually appears in Nature that forces us to introduce a second pair of \(\psi\)-components”. Weyl’s two-spinor version of the Dirac equation is a coupled system of equations requiring both Weyl spinors \(\psi_{L}\) and \(\psi_{R}\) in order to preserve parity. Weyl considerd massless particles in his two-spinor version of the Dirac equation.  In this case, the equations of the two-spinor version of Dirac’s equation decouple, yielding an equation for \(\psi_{L}\) and for \(\psi_{R}\). These equations are independent of each other, and the equation for the 2-component left-handed Weyl spinor \(\psi_{L}\) is called Weyl’s equation; it is applicable to the massless particle called the  neutrino[104], a spin \(\bfrac{1}{2}\) particle, that was discovered in 1956. Yang (1986, 12) remarks 