Demonstration by Simulation: Experimental Grounds for Helmholtz's Theory of Perception

Patrick McDonald
Program in the History and Philosophy of Science
University of Notre Dame
pmcdonal@nd.edu

Hermann von Helmholtz (1821-1894) developed a comprehensive theory of perception. It operated at the most general philosophical level, but also played a significant role in his experimental research in vision and hearing. Among the central themes, three clusters of issues stand out: 1). Laws/Causes/Forces; 2). Sign-theory of perception and theory of unconscious inferences; 3). Experimental inquiry as active intervention with phenomena. In attempting to sort out the roots of these themes, scholars have attempted to link Helmholtz with a set of philosophical commitments reflecting the influences behind his particular views on the three clusters. I attempt to show that these ideas live more closely to the ground. There is undoubetdly much that Helmholtz owes to philosophical predecessors such as Kant, Fichte, Locke and Mill. However, the search for his debt to particular philosophical currents sometimes obscures the central role of his scientific work in the origin, conceptual content, and practical significance of his theory of perception. This I wish to highlight. His philosophy and science of perception must be understood in the context of his practice, even if practice alone fails to exhaust the matter. This paper primarily aims to explicate Helmholtz, however it should also function as an indirect argument for the central place of experimental practice in the philosophy of science and perception. In addition this approach should help untangle several ambiguous issues in his theory of perception. One might start by asking why an avowed empiricist was so sceptical regarding the power of the senses to access nature.

More specifically I argue that experiment (theory and practice) is the glue that holds his theory of perception together. It plays four crucial functions. One, his arguments for his theory of perception appeal to and arise out of empirical and experimental research on the senses. This is not a novel opinion. However I think its significance has been somewhat misinterpreted. Two, the idea of experiment fulfills a critical gap both in his philosophical and scientific theories of perception. In short, the senses alone fail miserably to reach the nature of objective actuality. However he was no sceptic. The senses simply need (lots of) help in the form of active intervention and experimentation coupled with the discovery of law-like relationships/coordinations to achieve any knowledge of objects and events. Thus experiment plays a central conceptual role. It functions not only as a scientific technique, but also as a crucial general epistemological strategy, and a central component to any learning theory. Three, Helmholtz's experimental practice elaborates his theory of perception applying key components such as the sign theory and concept of unconscious inference. This provides a crucial set of examples indispensible for understanding his theories. On the other hand, the consequences of the theory help to explain why his experimental style took the shape it did. Fourth, the extensive experiments he conducted in his research on vision and hearing were crucial for the fine-tuning of his theory of perception in the course of his career. This fourth point does not get developed in this paper.

To clarify the third point above, I will focus on a series of experiments from Helmholtz's physiological acoustics in which he synthesized human vowel sounds to support his proposed explanation for human vowel production and perception. The two themes in his theory of perception that most clearly come through is that because the senses, in this case hearing, suffer essential limitations, new laboratory instruments are required to produce and analyse tones. By producing tones he could clearly specify the physical properties of their component parts. With his resonators he was able to amplify these signals to allow the perception of components never before accessible. Only in this way can he hope to pursue his explanatory project. This may not seem too surprising - that's what one does in an experimental science of the senses. However the research strategy of coordinating physical signals, physiological codes (signs), and psychological percepts (representations) in tight functional relations was emerging largely through the comprehensive synthetic projects represented by Helmholtz's On the Sensations of Tone (1863) and Handbook of Physiological Optics (1856, 1860, 1867 - each of three parts respectively). He played a major role establishing a methodological structure for the study of the senses that continues to exert a heavy influence.

This reveals that Helmholtz's experimental inquiries play a (if not THE) central role in developing his theory of perception from the ground up, in providing a coherent picture of the success that perception does indeed have grasping objective properties of nature while succeeding to direct action, and in elaborating an enduring methodological framework.