of psychoanalysis Freud follows the psychology of Extraversion, Adler that of Introversion. The irreconcilable opposition between the views of Freud and those of Adler (see especially his book "Über den nervösen Charakter") is readily explained by the existence of two diametrically opposed psychological types which view the same things from entirely different aspects. An Extrovert can hardly, or only with great difficulty, come to any understanding with an Introvert, on any delicate psychological question. An Extrovert can hardly conceive the necessity which compels the Introvert to conquer the world by means of a system. And yet this necessity exists, otherwise we should have no philosophical systems and dogmas, presumed to be universally valid. Civilised humanity would be only empiricists and the sciences only the experimental sciences. Causalism and empiricism are undoubtedly mighty forces in our present-day mental life but it may come to be otherwise. This difference in type is the first great obstacle which stands in the way of an understanding concerning fundamental conceptions of our psychology. A second objection arises from the circumstance that the constructive method, faithful to itself, must adapt itself to the lines of the delusion. The direction along which the patient develops his morbid thoughts has to be accepted seriously, and followed out to its end; the investigator thus places himself at the standpoint of the psychosis. This procedure may expose him to the suspicion of being deranged himself; or at least risks a misunderstanding which is considered terribly disgraceful--he may himself have some world-philosophy! The confirmation of such a possibility is as bad as being "unscientific." But every one has a world-philosophy though not every one knows he has. And those who do not know it have simply an unconscious and therefore inadequate and archaic philosophy. But everything psychological that is allowed to remain in the mind neglected and not developed, remains in a primitive state. A striking instance of how universal theories are influenced by unconscious archaic points of view has been furnished by a famous German historian whose name matters to us not at all. This historian took it for granted that once upon a time people propagated themselves through incest, for in the first human families the brother was assigned to the sister. This theory is wholly based upon his still unconscious belief in Adam and Eve as the first and only parents of mankind. It is on the whole better to discover for oneself a modern world-philosophy, or at least to make use of some decent system which will prevent any errors of that kind. One could put up with being despised as the possessor of a world-philosophy; but there is a greater danger. The public may come to believe the philosophy, beaten out by the constructive method, is to be regarded as a theoretical and objectively valid insight into the meaning of the world in general.