Douglas, A. (2015) Was Spinoza a naturalist? Pacific Philosophical Quarterly, 96, 77–99. doi:10.1111/papq.12
[Abstract]In this article I dispute the claim, made by several contemporary scholars, that Spinoza was a naturalist. ‘Naturalism’ here refers to two distinct but related positions in contemporary philosophy. The first, ontological naturalism, is the view that everything that exists possesses a certain character (variously defined) permitting it to be defined as natural and prohibiting it from being defined as supernatural. I argue that the only definition of ontological naturalism that could be legitimately applied to Spinoza’s philosophy is so unrestrictive as to tell us nothing about the content of his ideas. The second, methodological naturalism, is the view that the natural sciences are the best means of finding out substantial truths about the concrete world. I present some historical research showing that Spinoza’s way of positioning himself with respect to other philosophers in the Dutch Republic casts very serious doubt on the claim that he was a methodological naturalist. This adds further weight to arguments that have already been made against the naturalist reading of Spinoza.
[Citing Place (1956)]  
Citing Place (1956) in context (citations start with an asterisk *):
Section Ontological Naturalism
* Some scholars [...] have argued that, despite apparent objections arising from the attribute of thought, the proper reading of the Ethics [by Spinoza] in fact reveals a physicalist vision of reality. Edwin Curley, for example, argues that since Spinoza claimed that each mode of thought is identical with some mode of extension he in fact held the view that everything in the world is physical, including mental states, which are ultimately reducible to bodies or bodily affections. Curley is presumably interpreting Spinoza as a physicalist along the lines of the view espoused by identity theorists such as U. T. Place [(1956)] and J. J. C. Smart [(1959)]. Michael Della Rocca, however, denies that Spinoza should be read as a physicalist of this kind. He stresses that, unlike modern identity theorists, Spinoza did not believe that ‘the mental properties of a thing are to be completely explained by and depend on its physical properties which are in some sense more fundamental’.