But when we come to ask _what_ disease of the nerves, or, more strictly, of the nervous system, is implied in speaking of the “neuropathic” we find no satisfactory answer. Certainly no one disease is regarded as being the causal factor. And the list of theories is overwhelming. Disturbances of the genital, vaso-motor, or digestive systems, demineralisation, chemical disturbances of nutrition of hepatic or cholæmic origin, visceral ptosis, cerebellar disturbance, thyroid disorder, complex disturbances in functioning of the blood vessels, intoxication, exhaustion[60]: these are some of the numerous theoretical suggestions proposed to account for neurasthenia only. Whether the unfortunate neuropath is supposed to be afflicted by one or all of these is a matter which we certainly cannot decide; for the theories proceed from many different sources. But we must not lose sight of another important fact in this connection. The neuropathic person’s mental troubles, or those at least for which he seeks relief from the physician are by no means in the clouds of theory. They are real enough, and as a rule not to the patient only, but also to his relatives and friends, with whom he finds it difficult to live amicably. Those troubles are based upon fear, anxiety, anger, and excessive curiosity concerning matters about which the normal person would not bother his head. They find expression in outbursts of pugnacity or of unusual self-assertion with its emotion of elation, often followed by self-abasement and subjection, inordinate desires either to be alone or never to be alone, floods of tender emotion, possibly following close on the heels of a mood of blatant self-assertion with no regard for the feelings of others. These relatively simple processes of mind, occurring sometimes in comparative isolation, sometimes inextricably blended or kaleidoscopically transient, are the real marks of the so-called neuropath or neurotic. Bodily troubles may, and often are, added to these. But as every physician knows to his cost (and sometimes to the patient’s), and as faith-healers know to their advantage, these bodily diseases are usually exaggerated by the neurotic sufferer, and frequently prove to have but a slight material basis. In other words, the real marks of the “neurotic” are mental.[61] And one need not be a technical psychologist to see that the above list is nothing but an enumeration of the instincts and emotions possessed in common by all men.[62]