The latter reflection shows us, however, that in certain cases, at least, there is a certain difference in degree between neuroses and psychoses. The evolution of the human mind has been formed by degrees, by successive stages, and we possess in ourselves a series of superposed layers which correspond to diverse stages of the psychological development; when our forces diminish we lose successively these diverse layers commencing with the highest. It is the superior floors of the buildings that are reached first by the bombardments of the war and the cellars are not destroyed at first; they acquire even more importance, as people are beginning to inhabit them. Well, according as the depression descends more or less deeply, the disorders which result from the loss of the superior functions and the exaggerated action of the inferior ones become more and more serious and are appreciated differently. The superior psychological functions are, in my opinion, experimental tendencies and rational tendencies. They are tendencies to special actions in which man takes in account remembrances of former acts and of their results, in which he enforces on himself by a special effort obedience to logical and moral laws. A little fatigue and a slight degree of exhaustion are sufficient for such an action to become difficult and impossible to prolong for a long time. Furthermore, the disorders of the experimental conduct or of the rational conduct are very frequent. These disorders only reach the superior actions which are not absolutely necessary to the conservation of social order. They can be easily repaired by inferior acts: if the man does not obey pure moral principles, at least he can conduct himself in appearance in an analogous manner through fear of the prison. Also, these disorders of the superior functions are considered as slight; they are called errors, or faults, and it is admitted that the subjects remain normal beings.