Aspects of modern physics, such as the hypothetical tachyon particle and certain time-independent aspects of quantum mechanics, may allow particles or information to travel backward in time. Logical objections to macroscopic time travel may not necessarily prevent retrocausality at other scales of interaction.
Gestalt and Universals This brief chapter is a philosophical enquiry into the relationship between the physical events in the central nervous system and the subjective experiences of the individual. It concentrates principally on the processes whereby nervous signals from the retina are transformed into a representation of the visual field. It also explores the various feedback loops involved in the operation of the eyes: the homeostatic operation of the retina to control light levels, the adjustment of the lens to bring objects into focus, and the complex set of reflex movements to bring an object of attention into the detailed vision area of the fovea. The chapter concludes with an outline of the challenges presented by attempts to implement a reading machine for the blind.