physician to maintain the life of his patients as long as he can in all circumstances. I should like to know why. While I am dealing with this important and--for the medical conscience--difficult question of social ethics, I may take the opportunity to consider the general attitude of physicians to the monistic philosophy. It is now half a century since I visited the wards in the Julius hospital at Würtzburg as a medical student. It is true that--happily for me and my patients!--I practised the profession only for a short time after I had passed my examinations in 1857; but the thorough acquaintance with the human organism, its anatomic structure and physiological functions, which I then obtained has been of incalculable service to me. I owe to it not only the solid empirical foundation of the special study of my life, zoology, but also the monistic tendency of my whole system. As the medical training in its widest sense includes anthropology--and so should include psychology also--its value for speculative philosophy cannot be exaggerated. The scholastic metaphysicians who still regard the chairs of philosophy at our universities as their monopoly would have avoided most of their dualistic errors if they had had a thorough training in human anatomy, physiology, ontogeny, and phylogeny. Even pathology, the science of the diseased organism, is very instructive for the philosopher. The psychologist especially acquires, by the study of mental disease and the visiting of the asylum wards, a profound insight into the mental life which no speculative philosophy could give him. There are few experienced and thoughtful physicians who retain the conventional belief in the immortality of the soul and God. What would the immortal soul do on the other side of eternity when it is already utterly ruined in this life, or was even born as an idiot? How can a just God condemn the criminal to the fires of hell when he himself has tainted the man with an hereditary bias, or has placed him in an environment in which, seeing the absence of free-will, crime was a necessity for him? And how can this all-loving God answer for the immeasurable sum of want and misery, and pain and unhappiness, which he sees accumulated before him every year in the lives of families and states, cities and hospitals? It is no wonder that the old saying ran: _Ubi tres medici, duo sunt athei_ (Of three doctors two are sure to be atheists). One of my medical colleagues was an old, experienced, and sympathetic physician who had travelled all over the world, and had then, as director of a large hospital, been a close witness of the sufferings of humanity. Religiously educated by pious parents, and endowed with keen sensitiveness, he was, after long struggles, forced by his medical studies to part with the faith of his boyhood--like myself, in his twenty-first year. We were talking about the great mysteries of life shortly before his death, and he said to me: "I have been unable to