Yet all these halfway external advantages count little compared with the significance and importance of the topic for the inner life of scientific thought of our time. We all felt it was the one topic which the beginning of the twentieth century demanded and which could not be dealt with otherwise than by the combined labors of all nations and of all sciences. The World's Fair was the one great opportunity to make a first effort in this direction; we had no right to miss this opportunity. Thus it was decided to have a congress with the definite purpose of working towards the unity of human knowledge, and with the one mission, in this time of scattered specializing work, of bringing to the consciousness of the world the too much neglected idea of the unity of truth. To quote from our first tentative programme: "Let the rush of the world's work stop for one moment for us to consider what are the underlying principles, what are their relations to one another and to the whole, what are their values and purposes; in short, let us for once give to the world's sciences a holiday. The workaday functions are much better fulfilled in separation, when each scholar works in his own laboratory or in his library; but this holiday task of bringing out the underlying unity, this synthetic work, this demands really the coöperation of all, this demands that once at least all sciences come together in one place at one time." Yet if our work stands for the unity of knowledge, aims to consider the fundamental conceptions which bind together all the specialistic results, and seeks to inquire into the methods which are common to various fields, all this is after all merely a symptom of the whole spirit of our times. A reaction against the narrowness of mere fact-diggers has set in. A mere heaping up of disconnected, unshaped facts begins to disappoint the world; it is felt too vividly that a mere dictionary of phenomena, of events and laws, makes our knowledge larger but not deeper, makes our life more complex but not more valuable, makes our science more difficult but not more harmonious. Our time longs for a new synthesis and looks towards science no longer merely with a desire for technical prescriptions and new inventions in the interest of comfort and exchange. It waits for knowledge to fulfill its higher mission, it waits for science to satisfy our higher needs for a view of the world which shall give unity to our scattered experience. The indications of this change are visible to every one who observes the gradual turning to philosophical discussion in the most different fields of scientific life.