 For a scalar wave function, describing particles without spin, the form of  the guiding equation  above is a little more complicated than necessary, since the complex conjugate of the wave function, which appears in the numerator and the denominator, cancels out. If one looks for an evolution equation for the configuration compatible with the space-time symmetries of Schrödinger’s equation, one almost immediately arrives at the guiding equation in this simpler form as the simplest possibility.