We talked nonsense, we did absurdities, we had invented a language of our own, we flung the most shocking insults at each other, we had the wildest romps and the most extraordinary songs, we played, not indeed with dolls, but with creatures of our fancy; in short, we were silly, silly, happy children. I embodied this phase of our life in a monograph entitled _Es Löwos_, which appeared first in the Munich monthly _Die Gesellschaft_, and then in book form. Many reproached me for it, saying, “One does not expose such privacies to the multitude.” As if one wrote for the multitude! One always imagines as one’s readers those in whom a string tuned to the same note is vibrating. There are never more than a few such in the multitude. In _Es Löwos_ I went so far as to imagine only one, and always apostrophized as “One” this sympathetic, comprehending person, who perchance had experienced the like in his own life. And lo and behold! in the course of time I received something like a hundred letters from the reading public, in which the writers assured me that they had had all my experiences, and signed themselves “The One.” Our studies had opened to us a new horizon, I said just now. That must be enlarged upon a little. It was especially through the natural sciences that undreamed-of lights broke upon our minds. But not as they were usually taught in the schools, mere classifications of plants and animals into species and orders, mere enumerations of mineralogical and geological formations, mere dry elements of physics and chemistry with their proper figures and symbols; no, we gained our knowledge from the works of the latest students of nature, those who are also philosophers of nature, and from whose investigations bursts the radiance of a new discovery, namely, that our whole glorious world is subject to the law of evolution. By evolution from the simplest origins it has developed into its present complexity and is assured of incalculable transformations yet to come. Then these other truths perceived by modern science, the transmutability of all forces one into another, the unbroken concatenation of all causality, the indestructibility of atoms, the uninterrupted continuity between the inorganic and the organic world, between physical and psychical life,—in short, the unity of the world, and the consequent inference that the development of human society also goes on in accordance with the same laws and that it also is assured of incalculable future transformations.