Brian L. Keeley

How ought we differentiate the senses? What, say, distinguishes vision from audition? The question comes in two versions. First, there is the traditional problem of individuating the senses in humans. Second, there is also an important question about what sensory modalities we ought to attribute to non-human animals, a version of the question that has been virtually ignored by philosophers. Modality ought to be construed as an “avenue into” an organism for information external to the central nervous system. Six proposed criteria found in the philosophical literature concerning the senses are reviewed. Initially, four criteria—physics, neurobiology, behavior, and evolutionary or developmental dedication—are shown to be individually necessary and jointly sufficient. Next, two criteria—Aristotle's proper objects of sensation criterion and Grice's sensation or qualia criterion—are considered and rejected. One overarching goal here is to show that there is interesting contemporary work left to be done on this ancient philosophical question.