Spinoza's own view is one according to which human beings and the rest of reality are not explained in such different ways, according to which human beings and all else operate according to the same laws. Such a unification of explanatory principles is the heart of Spinoza's naturalism about psychology: human psychology is governed by the same fundamental principles that govern rocks and tables and dogs. Thus no new principles are needed to explain human psychology beyond those principles needed to explain the rest of nature anyway. More generally, Spinoza's naturalism, as I understand it, is the view that there are no illegitimate bifurcations in reality.

Spinoza (2008) - One: Spinoza's Understanding and Understanding Spinoza