Critical Remarks on Physiological Interpretations of the Apriori

“It follows from the analysis of our sense perceptions that there are, actually, no qualities”. Emil Du Bois-Reymond grounded his claim (1872, 445) on the then knowledge of nerve activity, yet he also introduced “sense substances” translating stimulations into sensations and bearing “specific energies”. In brief, sensation is a transcendent, “unconditional” limit of natural knowledge, but (our) knowledge depends on it and scientists do attempt to account for it. Interpretations of sense physiology were provided in a programmatic Kantian key, also based on the notion of ‘sense energies’, which was to bridge the gap between mechanical explanations of the sensorium and the appearing of sensory qualities. Sense physiology thus seemed to “develop” and “confirm” Kant’s theory of the a priori. In how far was such claim legitimate? After dissecting Du Bois-Reymond’s statements, I test their consistency and contextualise them within the state-of-the-art of sense physiological research in the second half of the 19th century. Grounding on these analyses, I argue that the notion of ‘specific energies’ coheres neither with mechanical basics of knowledge (according to Du Bois-Reymond’s account) nor with Kantian interpretations of physiological theories – thus testifying once more to a lack, if not to the impossibility of knowledge regarding sensation.