In The Realistic Empiricism of Mach, James, and Russell, Eric Banks attempts to revitalize the theory of ‘neutral monism’ (or ‘realistic empiricism’), a philosophical position developed through the works of Ernst Mach, William James, and Bertrand Russell. This theory, which basically states that the fundamental constituents of the world are neither mental nor physical but ‘neutral,’ is both an underappreciated position in the history of philosophy and one which has value in contemporary philosophy of mind. By reviving and further developing this thesis, Banks attempts to contribute both to the history of the ‘scientific philosophy’ of the early 20th century and modern debates on supervenience and physicalist explanations.
Chapters 1 and 2 contribute to the recent resurgence of interest in Mach’s work by reconstructing his theory of the elements and philosophy of mind. Mach’s motivation to provide empirical explanations of psychological phenomena, in contrast to Brentano’s ‘intentionality’ view, led him to formulate a monist theory on which both psychological and physical phenomena can be metaphysically united. For Mach, the most fundamental constituents of the world are elements understood as individual events which come in and out of existence. The fact that they are fleeting makes them too difficult to be known directly, but we still come to recognize certain patterns in nature (i.e., laws) which provide knowledge of the elements. These elements are manifestations of dynamical powers (or causal forces) and are always in some sort of functional dependence (i.e., causal relation) with other elements. What makes an element ‘mental’ or ‘physical’ is its functional dependence; a mind-independent element embedded in functional dependencies with other mind-independent elements is ‘physical’ and a mind-independent element being perceived (i.e., in a functional dependence with a brain) is ‘mental.’ The dualism between the mental and the physical is thus not a dualism within elements themselves, but a statement of the functional dependencies those elements are in.
This forms the basis of Mach’s metaphysics, which Banks goes on to contrast with a variety of other positions. Mach’s view is not phenomenalist, as often thought, since he admits that mind-independent elements exist and their nature is not dependent on our sensations. He is not a neo-Humean about causation since we know causes directly. He is not a Kantian since there is no ‘thing-in-itself’ which underlies our experience. And, most importantly, Mach is not a positivist. Herein lies one of Banks’ most important historical insights. Mach has often been discredited as a primitive positivist, who served as a historical stepping stone for the logical empiricists. Against this reading, Banks points to several differences between the two positions: Mach intends to provide a first-order ontology whereas the logical empiricists intended to provide a second-order methodology; Mach’s famed opposition to atoms was not simply that they were unverifiable (as the logical empiricists thought), but that atoms were conceived of being in principle unconnected with experience; and Mach’s criticism of mechanist philosophy was not simply an ‘anti-metaphysics’ stance, but that it is suspect because it assumes that the real world must somehow line up with our intuitive visualizations of it. Mach’s view, as Banks rightly points out, is much more interesting than normally thought and his views still have relevance in a post-positivist philosophy of science.
Chapters 3 and 4 reconstruct James’ and Russell’s contributions to Neutral Monism respectively. Banks’ spends the majority of Chapter 3 reconstructing James’ direct realist view of perception which contains four primary theses: (1) sensations (as they appear) are real, have no representational intermediary and are neither true nor false, (2) acts of perception are distinguished from judgments about perception (which are true or false), (3) judgments of objects of perception can only be asserted if those objects are mind-independent (i.e., we cannot make judgments about the objects of illusions), and (4) the act of perception is causally-linked to external objects. This fills in Mach’s missing view of perception. Here, there is no ontological distinction between appearance and reality since both are results of different causal chains. Chapter 4 revisits an often-underexplored segment of Russell’s career (1919-1927) where Russell abandoned his theory of acquaintance and adopted a form of neutral monism. While Russell’s view is not completely in-line with James’ and Mach’s (he holds a representational view), he contributes to the project with his structural realist view of space. Here, Russell attempts to construct an abstract view of space out of ‘event particulars’ (which are synonymous with Mach’s elements) in which event particulars become known through the causal relations in which they are embedded. This spells out, in greater detail, what Mach attempted to achieve with his notion of a ‘causal-functional map’ where we can trace the functional dependencies of individual events.
Chapter 5 contains Banks’ attempt to show the contemporary relevance of neutral monism. Here, he compares ‘enhanced physicalism’ (neutral monism) with the standard physicalist approach in philosophy of mind. This provides two main insights. First, enhanced physicalism is able to ground physicalist conceptions of supervenience (specifically Kim’s). For Kim, supervenience occurs when some event ‘e’ instantiates some mental property Mx at t, due to the instantiation of some physical property Px but is silent about what actually instantiates Mx and Px. This makes events identical if they have both Mx and Px. Enhanced physicalism grounds this relation in elements which allows for a more accurate comparison of events. Second, enhanced physicalism encourages a posteriori explanations of events rather than a priori explanations which hold that some macro-event can be explained by taking a function (composed of causal knowledge) of some set of micro-events. A posteriori explanations do not assume that macro-events can be deduced in this fashion; the Px/Mx relation is identical qua causal powers but non-identical qua manifestation since Px and Mx cannot be co-occurring. This argument, however, relies on the controversial premise that Px and Mx cannot be concurrent. Banks’ grounds this argument on the empirical fact that, when neurons of a particular configuration are measured, the associated mental event disappears. However, this seems to be the case only because the measuring devices stand in a particular causal relation to the mental event. Presumably, this configuration could be observed without making the mental event disappear thus giving us Mx and Px simultaneously. Barring this issue, these two arguments help extend and refine physicalism.
In Chapter 6, Banks’ contributes to the neutral monist project himself by giving it a notion of extension and space (which neither Mach nor Russell could do). The challenge is to construct extension out of elements without being circular or assuming it as a basic intuition (as Kant did). Here, Banks argues that Hermann Grassman, a 19th century mathematician, has provided a point-algebra that provides a suitable notion of extension. Extension comes from tracing various associative and dissociative relations between points (much like Mach’s functional dependencies of elements). Points, then, do not exist ‘in’ space since those points are merely symbolic. Space and extension, then, are constructed out of this process of ‘tracing.’
Banks’ book delivers what it promises. It provides a novel interpretation of Mach, which should be of great interest to philosophers of science, and provides a more detailed reconstruction of some of James’ and Russell’s views than has previously been given. While it remains questionable whether neutral monism can completely supplant traditional physicalism as the argument for the lack of concurrence of Mx and Px is left underdeveloped, it still provides a novel approach which seems initially plausible, philosophically interesting, and has a wide range of potential applicability.
