H O N O R A R Y D O C T O R A T E S P E E C H I N M A D R I D 8 9 1 sí solos, no podrían crear una ciencia experimental (Erfahurungs-Wissenschaft) mejor que los empíricos puros. La solución está en la compenetración armónica de espíritus orienta- dos de diferente manera. Hago votos por que salgan de vuestra Universidad investigadores activos de ambas cla- ses que anmenten y profundicen los conocimientos humanos. TRANSLATION EINSTEIN’S S PEECH So many are the honors and testimonies of warm sympathy that have been bestowed on me during my stay in Madrid that I hardly find words to express my gratitude. I only want to say that due to this doctor honoris causa nomination by your university, I feel a close bond to it and I will take as much interest in its prosperity as those who were initiated in science here. You have pondered my scientific research, which you deem successful, so deeply and carefully that I do not need to add anything else in this regard. Maybe on this occasion, it would be better for us to consider the internal forces that promote scientific investigation and drive us to positive results, and how we appreciate them. In my judgment, the answers to these questions will be very different depending on the temperament of the researcher. All have in common the ideal of a comprehensive intellectual mastery of all the empirically known diversities by means of a system of generic concepts (Begriff-System), applied as uniformly as possible. However, the preferred tendency of some of them is directed toward the thorough knowledge of the diversities of science, whereas for others, toward its unifi- cation. I belong to the most extreme representatives of this latter tendency. The isolated fact does not interest me unless it is related to the fundamental system of ideas. For example: as soon as I was convinced of the exactitude of the hydrodynamic equations in a particular case, I did not care for the hydrodynamical problems unless they could broaden something in the sphere of action of this system of equations. The same happens to me in every area. This bias of interest that emerges from a profound, almost religious, belief in the unity and simplicity of the principles of the structure of the Universe, has determined all my scientific work. This belief has given me the strength to dedicate all my activity to the study of problems that appear to be almost insoluble despite long years of frustrated attempts. Men such as I could not create an experimental science (Erfahrungs-Wissenschaft) on their own better than the pure empiricists. The solution is the harmonious cooperation of differently orient- ed minds. I solemnly hope that your university will bring forth productive researchers of both cat- egories who will increase and deepen human knowledge.