No mere machine can build up itself, can make any remote approach to metabolism as an organized body can; and the principle of this immanent action is not matter itself, because it uses, makes, subordinates matter to itself. That principle is positively one, not one by continuity as matter is. Matter as in a crystal grows by mere aggregation, an organism grows by assimilation; a crystal loses force in formation and growth, an organism accumulates force.
The theory that denies the existence of this formal principle does not explain the phenomena of life in organic beings. Uniformity of tendency toward an end is not a characteristic of mere matter; neither is a harmonious interaction of parts, nor the dependence of parts on the unit, nor motion, nor the reproduction of the species.
Moreover, most of the greatest physical scientists strongly maintain that there must be a formal substantial principle in all living things. Among these are Wallace, Nägeli, Askenasy, Preyer, Fechner, Agassiz, von Baer, E. de Beaumont, Blanchard, A. Braun, Brongniart, Bronn, Burmeister, Delff, Milne-Edwardes, Flourens, Goeppert, Griesbach, Heer, Koelliker, Mivart, Quatrefages, Quenstedt, Spiers, Volger, R. Wagner, Liebig, and Joseph Hyrtl.
The formal principle which coexists with matter in the organic body is really though not perfectly distinguished from matter. A formal principle which is necessary for sensation should be either perfectly simple, or at the least so one that its parts together make up one essence: matter, however, cannot have such unity, and as a consequence the formal principle must be distinct from matter. Anything is like its operation, and the parts of any sensitive activity always result in an activity that is essentially one. If we touch a table, by that single touch we at once know that the object is one, wooden, hard, angular, smooth, extended, and so on, and we also know that one subject perceives all these varied qualities. One eye can convey knowledge at once of a thousand objects miles apart, and these objects can be brought into one perception only by a simple subject. An extended complex subject like matter would get one impression (if it could perceive any impression) on one side, one on another, and so on, but it could not unite these.