The content of this section will be more clearly understood if a few of the introductory remarks to the later section on psychiatric diseases are anticipated here. The main thesis of the neurologist is that mental and physical functions of the nervous system are simply two aspects of the same neural process. Mind and behavior both have their roots in the self-regulating, goal-seeking activities of the organism, the same ones that provide impulse to all forms of mammalian life. But the prodigious complexity of the human brain permits, to an extraordinary degree, the solving of difficult problems, the capacity for remembering past experiences, and casting them in a symbolic language that can be written and read, and the planning for events that have yet to take place. The constant but sometimes meandering internal verbal experience of this ideation during waking was aptly named "stream of thought" by William James. Somehow there emerges in the course of these complex cerebral functions a continuous awareness of one's self, and the operation of one's psychic processes. It is this continuous inner consciousness of one's self, of one's past experiences, and of ongoing cognitive activities that might be called mind. Whether this is an emergent property of various mental functions or simply their representation cannot be answered, but any separation of the mental from the observable behavioral aspects of cerebral function is probably illusory. Biologists and psychologists have reached this view by placing all known activities of the nervous system (growth, development, behavior, and mental function) on a continuum and noting the inherent purposiveness and creativity common to all of them. The physician is persuaded of the truth of this view through daily clinical experience, in which every possible aberration of behavior and intellect appears at some time or other as an expression of cerebral disease. Furthermore, in many brain diseases, one witnesses parallel disorders of the patient's behavior and a dissolution or distortion of the introspective awareness of his own mental capacities.