Perceiving the Present: Systematization of Illusions or Illusion of Systematization?


should be sent to Robert E. Briscoe, Department of Philosophy, Ohio University, Athens, OH 45701. E-mail:


Mark Changizi et al. (2008) claim that it is possible systematically to organize more than 50 kinds of illusions in a 7 × 4 matrix of 28 classes. This systematization, they further maintain, can be explained by the operation of a single visual processing latency correction mechanism that they call “perceiving the present” (PTP). This brief report raises some concerns about the way a number of illusions are classified by the proposed systematization. It also poses two general problems—one empirical and one conceptual—for the PTP approach.