As far as the question of the right to interpret nature teleologically is concerned, it would be entirely indifferent whether what Korschinsky calls “the tendency to progress,” and the system of laws in obedience to which evolution brings forth its forms, can be interpreted “mechanically” or not; that is to say, whether or not evolution depends on conditions and potentialities of living matter, which can be demonstrated and made mechanically commensurable or not. It may be that they can neither be demonstrated nor made mechanically commensurable, but lie in the impenetrable mystery inherent in all life. Whether this mystery really exists, and whether religion has any particular interest in it if it does, must be considered in the following chapter. CHAPTER VIII. THE MECHANICAL THEORY OF LIFE. What is life—not in the spiritual and transcendental sense, but in its physical and physiological aspects? What is this mysterious complex of processes and phenomena, common to everything animate, from the seaweed to the rose, and from the human body to the bacterium, this ability to “move” of itself, to change and yet to remain like itself, to take up dead substances into itself, to assimilate and to excrete, to initiate and sustain, in respiration, in nutrition, in external and internal movements, the most complex chemical and physical processes, to develop and build up through a long series of stages a complete whole from the primitive beginnings in the germ, to grow, to become mature, and gradually to break up again, and with all this to repeat in itself the type of its parent, and to bring forth others like itself, thus perpetuating its own species, to react effectively to stimuli, to produce protective devices against injury, and to regenerate lost parts? All this is done by living organisms, all this is the expression in them of “Life.” What is it? Whence comes it? And how can it be explained?