For Descartes and his contemporary successors, the cognitive subject exists in a domain that is separate from the real world of those substances and processes which serve as the objects of cognition. Reality itself is unknowable; at best we can achieve some cognitive grasp of models of reality, of surrogate worlds, which may or may not bear some relation to the reality beyond.

This Cartesian conception of knowledge and cognition has predominated not least in our understanding of databases and of the (semantic) relations between information systems and the world beyond. Computers, it is held, deal with data models, not with the substances and processes in reality. Recent developments in information technology, however, imply the need for a radically new conception of these matters. When the nurse's palm-top computer can sense directly and immediately the physico-chemical processes taking place in the body of the patient; when the soldier's palm-top computer can sense directly and immediately his geographical location and the chemical and biological properties of the surrounding environment; when the building contractor's palm-top computer can read directly and immediately the wiring and plumbing in your walls -- then we are no longer dealing with computers to be understood along Cartesian lines. Rather, we need a new sort of view, according to which information systems are, like people, embedded in the reality which surrounds them.