# A question in Dirac article about Dirac equation about a sentence

Why it is said $W$ should be linear partial time derivative so that wave function could be determined by initial wave function?

• It is said the wave equation must be linear in $W$ or $\partial/\partial t$. Not that $W$ should be "linear partial time derivative". – J-T Sep 14 '17 at 13:25

If the equation is not linear (say quadratic) in $\partial_t$, then one needs to know more about the initial condition than just the initial wavefunction.