deeper penetration into the subject, it is found that the essential condition for the process, which exists, is a component common to both factors, one of which in consequence can replace the other. It is the task of all scientific research to penetrate deeper and deeper into these relations, these connections and the order of succession of states and processes and to separate them into their individual components, and in this way gain a more thorough knowledge of the constancy of existence and happenings in the world. This analytical process, it is true, only advances very gradually, and we must accept for the present, especially in the complex biological processes, that a whole complexity of members appear conditioned, and that a complex aggregate is a condition of the whole process. We are not yet in the position to define the special components of the constituent processes. It is only step by step that we are able to differentiate the necessary from the accessory parts in these complexes. However, we are here only concerned for the present with a purely theoretical question and we may be permitted to say: If we maintain that the conception of condition has as an integral part the element of necessity and of relation to a special thing, then there are no substituting conditions. For then every condition for a state or process is of equal value. There is no justification to give more prominence to one condition and place it in the position of being the “_cause_.” If the cause is elevated, then it is done from some superficial motive. This is confirmed by a glance at the practical use of the term cause. The cases in which the cause is always at once clearly recognized and named without doubt or hesitation are those where a new factor is added to an already existing system of conditions, which bring about a process. When such a process is produced, the last added condition is considered as “cause.” A shock acts on an explosive body, the body explodes: the shock is considered the cause. An induction shock acts on a muscle, the muscle contracts; the induction shock is looked upon as the cause of the muscle contraction. To regard only the last added condition as being of especial importance to the taking place and the explanation for a process is, however, a standpoint which could satisfy only the most superficial of observers. In a scientific investigation such methods should play no rôle. For to every careful observer it must appear quite clear from the beginning, that the previously existing conditions have as great a value for the taking place of the process and its explanation as that last added.