Much has been written of late years about multi-personalities, until the impression has spread that the possession of a number of differing personalities is a special form of insanity. This is quite wrong. The sane, no less than the insane man has a number of personalities, and the difference between them lies in the power of co-ordination. The sane man is like a skilful driver who is able to control his team of horses; whereas the insane man has lost control of his steeds, and allows first one and then the other to get the mastery of him. The personalities are no more numerous than before, only we are made aware of their number. In a sense, therefore, every human being is complex. Inheritance and environment have left distinctive characteristics, which, if the power of co-ordination be weakened, take possession of the individual as opportunity may determine. We usually apply the term personality to the resulting blend of the various personalities in his nature. In the case of sane men and women the personality is a very composite affair. What we are thinking of frequently when we apply the epithet “complex” is a certain contradictoriness of temperament, the result of opposing strains of blood. It is the quality, not the quantities, of the personalities that affects us. If not altogether happy, the expression may in these cases pass as a rough indication of the opposing element in their nature. But when used, as it often is, merely to indicate an eccentricity, the epithet assumes a restricted significance. A may be far more complex than B; but his power of co-ordination, what we call his will, is strong, whereas that of B is weak, so we reserve the term complex for the weaker individual. But why reserve the term complex for a few literary decadents who have lost the power of co-ordination, and not apply it to a mind like Shakespeare’s, who was certainly as complex a personality as ever lived? Now I do not deny that it is wrong to apply the term complexity to men of unstable, nervous equilibrium. What I do deny is the right to apply the term to these men only, thus disseminating the fallacy—too popular nowadays—that genius and insanity are inseparable.