Mach and James on Neutral Monism and the Unity of Science

Erik C. Banks

Wright State University

According to Ernst Mach (in the Analysis of Sensations of 1886 and Knowledge and Error in 1905) and William James (in his Essays in Radical Empiricism, published beginning in 1904 with “Does ‘Consciousness’ Exist”) sensations, such as colors or sounds, are to be treated as neither mental nor physical, in the conventional sense, but as neutral phenomena, events as real as any in the natural world. This was why Russell later called the movement “neutral monism,” even before his own conversion to the view in 1918. The elements (as Mach called them), or pure experiences (as James called them) are found to vary with psychological phenomena such as memory images or associations and also to vary with physical phenomena, such as the lighting of a room or the condition of the retina or brain, and really belong in both orders. Both Mach and James believed that declaring sensations neutral was the way to unify psychology (or at least theories of perception) with physics and the neutrality thesis is thus the first step toward a genuinely unified philosophy of science. I will start by going over what we know about the Mach-James relationship, as practicing empirical psychologists and as scientist-philosophers (with special attention to their correspondence and their face to face meeting in Prague). I will then examine the neutrality thesis in detail, as each understood it, and show why they believed this was the essential step in overcoming the dualism separating psychology from physics, at least about sensations and their phenomenal qualities. I will then show why I believe that both Mach and James envisioned what I call an “enhanced physicalism,” which would expand our understanding of the physical, or natural, world to include experienced sensation (colors, sounds and all) as real natural brain events, and not exclusively mental or illusory. I will also show that this enhanced physicalism was not just phenomenalism warmed over; both men acknowledged that there had to be elements, and pure experiences, which were not anyone’s sensations but rather events in the mind-independent natural world (another feature of their position that has often been misunderstood). Neutral monism must rather be understood as a genuine, original, and very ambitious, attempt to frame a unified scientific world view which includes human experience and physics under the same roof. I will close by briefly comparing my own published work on this subject, beginning in 2003, with what other recent authors have had to say on the subject and identify some problems and puzzles for future inquiry.