The nervous system allows the relations that occur at the sensory surface to be embodied in a particular pattern of nervous activity. With the growth of the interneurons, this pattern no longer has a direct effect on the motor surface but constitutes a perturbation for the internal nervous system itself. The state of relative nervous activity becomes itself an object of interaction for the nervous system, leading to further activity. This is the basis for a further expansion of the cognitive domain, a domain of interaction with its own internal states as if they were independent entities. This is the beginning of what we term abstract thought.