The design of an interface between two systems depends upon the way in which the systems are understood and characterized by the designer. Digital computation and the concomitant understanding of cognition as a computational process allowed the interface to be developed as a surface of contact between two symbol-processing systems. This paper suggests that as embodied, situated and to an increasing degree autonomous artifacts are developed and as cognition becomes understood as a dynamical process that new forms of interface will be required. It is suggested that direct actions in the world are the most robust means of means of communication. This eliminates the interface as an object or artifact of design and concentrates efforts on crafting the interaction that takes place between autonomous agents.