The five senses of sight, hearing, smell, taste, and touch, enumerated by Aristotle, were incremented in the early nineteenth century by a muscle sense, multiple dimensions of touch, and a movement sense. Aristotle explicitly excluded a sixth sense, and five remains the number of senses in the popular imagination. The division of touch into several sensations was entertained and rejected by Aristotle, but it was given anatomical, physiological, and psycho-physical support in the late nineteenth century. A separate muscle sense was proposed in the late eighteenth century, with experimental evidence to support it. Before these developments, however, behavioral evidence of the vestibular sense was available from studies of vertigo, although it was not integrated with the anatomy and physiology of the bony labyrinth until the late nineteenth century. This talk outlines the history of the scientific search for a sixth sense and assesses the evidence adduced to support previous categorizations.