Nagel’s challenge is to devise an objective phenomenological vocabulary that can describe the objective structural similarities between aural and visual perception. My contention is that Charles Sanders Peirce’s little studied and less understood phenomenological vocabulary makes a significant contribution to meeting this challenge. I employ Peirce’s phenomenology to identify the structural isomorphism between seeing a scarlet red and hearing a trumpet’s blare. I begin by distinguishing between the vividness of an experience and the intensity of a quality. I proceed to (...) identify further points of structural isomorphism (a) between the experience of seeing a scarlet red and of hearing a trumpet blare and (b) between the qualities of those experiences. Lastly, I gesture towards how these distinctions can be an aid in describing what it is like to be a bat. (shrink)