  In early 1928 P. A. M. Dirac provided the first physically compelling theoretical account of the dynamics of an electron in the presence of an electric field. The components \(\psi^{i} (x)\) of Dirac’s four-component wave function or spinor field in  Minkowski space, \(\psi(x) = (\psi^{1}(x), \psi^{2}(x), \psi^{3}(x),  \psi^{4}(x))\), are complex-valued functions that  satisfy Dirac’s first-order partial differential equation and provide probabilistic information about the electron’s dynamical behaviour,  such as angular momentum and location. Prior to the appearance of  spinor fields \(\psi\) in Dirac’s equation, it was generally  thought that scalars, vectors and tensors provided an adequate system of mathematical objects that would allow one to provide a  mathematical description of reality independently of the choice of  coordinates or reference   frames.[98]  For example, spin zero particles \((\pi\) mesons, \(\alpha\) particles)  could be described by means of scalars; spin 1 particles (deuterons)  by vectors, and spin 2 particles (hypothetical gravitons) by tensors. However, the most frequently occurring particles in Nature are  electrons, protons, and neutrons. They are spin  \(\bfrac{1}{2}\) particles, called fermions that  are properly described by mathematical objects called  spinors, which are neither scalars, vectors or   tensors.[99]  Weyl referred to the \(\psi(x)\) in Dirac’s equation as the  “Dirac quantity” and von Neumann called it the  “\(\psi(x)\)-vector”. Both von Neumann and Weyl, and  others, immediately recognized that Dirac had introduced something  that was new in theoretical physics. v. Neumann (1928, 876) remarks: 