This negative dogmatism as to knowledge was rendered harmless and futile by the English philosophers, in that they maintained at the same time that everything happens exactly as if the intellect were a true instrument of discovery, and as if a material world underlay our experience and furnished all its occasions.  Hume, Mill, and Huxley were scientific at heart, and full of the intelligence they dissected; they seemed to cry to nature:  Though thou dost not exist, yet will I trust in thee.  Their idealism was a theoretical scruple rather than a passionate superstition.  Not so M. Bergson; he is not so simple as to invoke the malicious criticism of knowledge in order to go on thinking rationalistically.  Reason and science make him deeply uncomfortable.  His point accordingly is not merely that mechanism is a hypothesis, but that it is a wrong hypothesis.  Events do not come as if mechanism brought them about; they come, at least in the organic world, as if a magic destiny, and inscrutable ungovernable effort, were driving them on.

Thus M. Bergson introduces metaphysics into natural history; he invokes, in what is supposed to be science, the agency of a power, called the elan vital, on a level with the “Will” of Schopenhauer or the “Unknowable Force” of Herbert Spencer.  But there is a scientific vitalism also, which it is well to distinguish from the metaphysical sort.  The point at issue between vitalism and mechanism in biology is whether the living processes in nature can be resolved into a combination of the material.  The material processes will always remain vital, if we take this word in a descriptive and poetic sense; for they will contain a movement having a certain idiosyncrasy and taking a certain time, like the fall of an apple.  The movement of nature is never dialectical; the first part of any event does not logically imply the last part of it.  Physics is descriptive, historical, reporting after the fact what are found to be the habits of matter.  But if these habits are constant and calculable we call the vitality of them mechanical.  Thus the larger processes of nature, no matter how vital they may be and whatever consciousness may accompany them, will always be mechanical if they can be calculated and predicted, being a combination of the more minute and widespread processes which they contain.  The only question therefore is:  Do processes such as nutrition and reproduction arise by a combination of such events as the fall of apples?  Or are they irreducible events, and units of mechanism by themselves?  That is the dilemma as it appears in science.  Both possibilities will always remain open, because however far mechanical analysis may go, many phenomena, as human apprehension presents them, will always remain irreducible to any common denominator with the rest; and on the other hand, wherever the actual reduction of the habits of animals to those of matter may have stopped, we can never know that a further reduction is impossible.