Vision is one of the primary substrates for mediating interaction with the physical world. Imagine, for example, trying to walk around your house completely blindfolded. This is essentially the task a sensory-deprived robot would face trying to assemble an automobile. An index to every single component in the robot's world would be required, as would the recipe for using them. Such perfection is clearly impossible, as is walking around one's house without sensory information.
Feedback mechanisms are necessary to control uncertainty.
We take this relationship between vision, or the abstraction of descriptions from sensory information, and feedback, or differential activity toward a controlled end that depends upon these descriptions, to be fundamental. The nature of the description inferred will, of course, depend on the task, as will the extent of feedback. Analogously, security systems will need to be designed that track and, if possible, identify intruders. Different scanners, including CT, MRI, and PET, provide different views of biological tissue. Medically significant anomalies need to be identified and detected, and information from these different scanners integrated into a coherent presentation.