The Einstein-Kac lattice model of Brownian motion in one dimension is
extended to include massless particles which do not themselves scatter
, but which facilitate scattering of Brownian particles, The model is
completely classical and no formal quantization is employed. However b
y observing second-order effects in the distribution of Brownian parti
cles we recover directly the components of Dirac wave functions. Furth
ermore the probability densities describing the massless particles are
shown to form 'fields' which obey Maxwell's equations. This result ex
tends the context of the Dirac equation to include the physics of ense
mbles of classical particles with contact interactions. In this contex
t all 'quantum objects', including the wave function itself, are obser
vable in terms of distributions of particles on a lattice. (C) 1997 El
sevier Science Ltd.