could imagine the mechanism of the world to consist only of reversible processes, and that at a given instant the motions of all the particles of matter were reversed as a ball is knocked back, then the history of the material world would play itself over again backward. All that now happens would come to pass again after its time in the inverse order: the hen would become an egg again, the tree would grow backward into a seed, and after an infinite time the cosmos would be resolved again into chaos. What processes would now attend the reverse movements of the brain-molecules? If mental conditions depended only on arrangements of atoms, then with the same arrangements the same conditions would return, leading to surprising results; among them, that, always at the instant before we contemplate anything, the counterpart of it would happen. We may, however, spare ourselves from estimating the possibilities thinkable here. The crank of the world-machinery could not be thus turned backward. The motion of masses, for instance, which has been converted by friction into heat, could not be changed back again into the same amount of similarly adjusted, opposite-faced motion. The reversed world is a bit of impossible mechanical fancy-work, from which nothing can be drawn respecting the origin of consciousness and free-will.
Our seventh difficulty becomes no longer a difficulty, provided we determine to deny free-will, and to declare the subjective feeling of freedom a delusion; but otherwise it must be regarded as transcendent; and it is but a poor consolation to monism that it sees dualism entangled in the same net the more helplessly as it lays more stress on ethics. In this sense I once wrote, in the preface to my "Untersuchungen über thierische Elektricität" ("Researches on Animal Electricity"), the words upon which Strauss now appeals against me: "Analytical mechanics reaches to the problem of personal freedom, the solution of which must remain an affair of the abstractive faculty of each individual." But afterward—and I make no secret of it—the day of Damascus came to me. Repeated reflections on the subject of my public address, "Ueber einige Ergebnisse der neueren Naturforschung" ("On some Results of the Later Natural Philosophy"), led me to the conviction that at least three transcendental problems precede the problem of free-will, viz., besides the problem of the origin of matter and force, which I have previously defined, that of the first motion and that of the first sensation, in the world. That the seven world-problems have been counted out and numbered here as if in a mathematical book of examples, has come to pass in consequence of the scientific divide et impera. We might combine them into a single problem—the world-problem. The mighty thinker whose memory we honor to-day believed that he had solved this problem. He had arranged the world to his satisfaction. Could Leibnitz, standing on his own shoulders, take part in our reflections to-day, he would surely say with us, "Dubitemus.