causality. Who compelled you to imagine an absolutely primal condition of the world, and therewith an absolute beginning of the gradually progressing successions of phenomena—and, as some foundation for this fancy of yours, to set bounds to unlimited nature? Inasmuch as the substances in the world have always existed—at least the unity of experience renders such a supposition quite necessary—there is no difficulty in believing also, that the changes in the conditions of these substances have always existed; and, consequently, that a first beginning, mathematical or dynamical, is by no means required. The possibility of such an infinite derivation, without any initial member from which all the others result, is certainly quite incomprehensible. But, if you are rash enough to deny the enigmatical secrets of nature for this reason, you will find yourselves obliged to deny also the existence of many fundamental properties of natural objects (such as fundamental forces), which you can just as little comprehend; and even the possibility of so simple a conception as that of change must present to you insuperable difficulties.