This chapter proposes a return to theories of perception from the Age of Reason (17th–18th centuries) and asks if these theories have the potential to inform mobility technologies for visually impaired people. The inquiry begins with the Cartesian theory of perception and establishes that Descartes had conceived of the cane of the blind man as an instrument enabling access to new perceptions, on the condition that a perceptual learning intervenes, founded on the bypassing of divine laws regarding the union of the soul and the body. In this way, the Cartesian theory enables an account of the operation of more recent devices, such as Bach-y-Rita’s TVSS. However, this theory does not describe the way in which we learn to make use of the apparatus. It is for this reason the article then turns to the Condillacian theory of perception, which tasks itself with describing how the blind learn to perceive objects through the medium of a cane—namely, by gradually externalizing their sensations. Finally, Condillac’s theory is held up against that of Merleau-Ponty—one that is more frequently mobilized by contemporary researchers—in the aim of evaluating its theoretical and practical contributions.