Kinesthesis dates from 1880 but it implies sensitivity to movement whereas it ought also to imply information about the postures of the limbs and body. C. S. Sherrington, when he distinguished between proprioception and exteroception, in 1906, had a great insight. He suggested, and should have made us realize more fully, that an individual animal needs information about its own activities as well as information about the environment in order to function in the environment. The hypothesis being entertained is that there exists information for proprioception and that it can be registered. The adjusting of perceptual organs, the overt acts of attention in looking, listening, smelling, tasting, and touching, can be understood as an activity of extracting the invariants from potential stimulation, that is, the act of optimizing the pickup of external information. The ocular adjustments are continually producing new retinal images so as to pick up the potential information in light.