Against these and similar statements there would be no objection, if it could be shown that life really has its source in the material world. But if it can be demonstrated that life never does, nor ever could by any possibility, originate in lifeless matter, then it is evident that we must look for some other source. Let it be our object, then, fully to investigate this problem. If living beings are produced by material forces, experience must verify the fact that matter really creates life of itself. In other words, the “to be or not to be” of materialism is identical with the old question of _generatio aequivoca_ or _spontanea_, i. e., whether there exists in nature a spontaneous or parentless generation of living beings. _Generatio aequivoca_ covers the entire ground of the materialists. Here the doctrine has not only its principal roots but all of them. If the materialists lose this foothold, all their natural science resources are emptied at once, so important is _generatio spontanea_ for materialism. Only under this form and with this substance can natural science have anything in common with materialism, which latter, strictly speaking, is only a religious doctrine, although as such purely negative. But just for this reason science has for centuries labored to decide whether this doctrine is false or true. The question is, does or does not this spontaneous generation exist? Scientific research has, in all times, occupied itself with this question in different forms and modes. The farther we go back in time the more general we find the opinion that life may arise spontaneously from inorganic matter. That such an idea should prevail, is, of course, easy to understand. Very little was known about the propagation of the lower animals and plants. Especially the very peculiar and complicated development of the parasites and their passive migrations were practically unknown. It seemed impossible to understand whence these beings had come, so the nearest explanation was resorted to, that is to say, that wherever they were found, they had come into existence “of themselves.” Neither was it so clearly understood then as now that eggs and seeds are living beings as well as the fully developed animals and plants. It was thought that grain must decay in the earth, yea, that this was the necessary condition for the growth of the plant. Thus people had daily before their eyes cases where living beings were generated by substances that seemed inert and dead.