 Let us be more specific about this crucial problem. P. Pearle was the first to propose (Pearle 1990) a relativistic generalization of CSL to a quantum field theory describing a fermion field coupled to a meson scalar field enriched with the introduction of stochastic and nonlinear terms. A quite detailed discussion of this proposal was presented in (Ghirardi, Grassi &amp; Pearle 1990) where it was shown that the theory enjoys of all properties which are necessary in order to meet the relativistic constraints. Pearle’s approach requires the precise formulation of the idea of stochastic Lorentz invariance. 