The abstract propositions involved are these: -- First, that like units,subject to a uniform force capable of producing motions in them, will bemoved to like degrees in the same direction. Second, that like units if exposedto unlike forces capable of producing motion in them, will be differentlymoved-moved either in different directions or to different degrees in theSame direction. Third, that unlike units if acted on by a uniform force capableof producing motion in them, will be differently moved -- moved either indifferent directions or to different degrees in the same direction. Fourth,that the incident forces themselves must be affected in analogous ways: likeforces falling on like units must be similarly modified by the conflict;unlike forces falling on like units must be dissimilarly modified; and likeforces falling on unlike units must be dissimilarly modified. These propositionsmay be reduced to a still more abstract form. They all imply that in theactions and reactions of force and matter, an unlikeness in either of thefactors necessitates an unlikeness in the effects, and that in the absenceof unlikeness in either of the factors the effects must be alike.
When they are thus generalized, the dependence of these propositions onthe persistence of force is obvious. Any two forces that are not alike, areforces which differ either in their amounts or directions or both; and bywhat is called the resolution of forces, it may be proved that this differenceis constituted by the presence in the one of some force not present in theother. Similarly, any two units or portions of matter which are unlike insize, form, weight, or other attribute, can be known as unlike only throughsome unlikeness in the forces they impress on us; and hence this unlikenessalso, is constituted by the presence in the one of some force or forces notpresent in the other. Such being the common nature of these unlikenesses,what is the corollary? Any unlikeness in the incident forces, where the thingsacted on are alike, must generate a difference between the effects; since,otherwise, the differential force produces no effect, and force is not persistent.
Any unlikeness in the things acted on, where the incident forces are alike,must generate a difference between the effects; since, otherwise, the differentialforce whereby these things are made unlike, produces no effect, and forceis not persistent. While, conversely, if the forces acting and the thingsacted on are alike, the effects must be alike; since, otherwise, a differentialeffect can be produced without a differential cause, and force is not persistent.
Thus these general truths being necessary implications. of the persistenceof force, all the re-distributions above traced out as characterizing Evolutionin its various phases, are also implications of the persistence of force.
If of the mixed units making up any aggregate, those of the same kind havelike motions impressed on them by a uniform force, while units of anotherkind are moved by this uniform force in ways more or less unlike the waysin which those of the first kind are moved, the two kinds must separate andintegrate. If the units are alike and the forces unlike, a division of thedifferently affected units is equally necessitated. Thus there inevitablyarises the demarcated grouping which we everywhere see. By virtue of thissegregation, growing ever more decided while there remains any possibilityof increasing it, the change from uniformity to multiformity is accompaniedby a change from indistinctness in the relations of parts to distinctnessin the relations of parts. As we before saw that the transformation of thehomogeneous into the heterogeneous is inferable from that ultimate truthwhich transcends proof; so we here see that from this same truth is inferablethe transformation of an indefinite homogeneity into a definite heterogeneity.
