Physical look at vacuum fermionic charge

Using general principles, we present a simple physical derivation of the formula for the induced vacuum charge in 1+1 dimensions, and give some criteria for the dependence of that charge on the details of the background-field configuration. We also clarify some issues concerning the bosonization method, the dependence of the charge on the regularization procedure, and the connection with anomalies, and generalize the above discussions to higher dimensions.