MODERN- PHILOSOPHICAL BIOLOGY. 605 



" an ultimate analysis brings us down," and on which " a rational syn- 

 thesis must build up." From this first principle come as consequences 

 two correlative principles, viz. : uniformity of law, which is simply 

 the persistence of the relations between forces, manifested under iden- 

 tical forms and conditions ; and the principle of the equivalence of 

 forces, inductively established within the last twenty years. The 

 researches which resulted in the establishment of this principle rest 

 implicitly on the persistence of force, inasmuch as they measure all the 

 precedent forces, which have disappeared, and all the consequent foi'ces, 

 which have been produced, by the aid of a unit supposed to be con- 

 stant. If we add two other corollaries, the one relating to the direc- 

 tion of motion in the line of least resistance, the other to the form of 

 motion, which is always rhythmic, we have, with the principles of the 

 continuousness of motion and of the indestructibility of matter (these 

 representing under two correlative forms the principle of the persist- 

 ence of force), the sum total of the primary truths which serve as a 

 basis for knowledge in general. But these principles, however general, 

 are only analytical truths ; though they are essential to a philosophy, 

 they do not constitute a philosophy. They are the laws of the action 

 of forces separately considered. The universal synthesis which is to 

 constitute philosophy must express the total operation accomplished by 

 the cooperation of these factors. The law wliich shall formulate this 

 synthesis must be a law of the changes in forces under the two phases, 

 matter and motion, by which they are manifested to us: it must be 

 a principle of dynamics holding good both for the whole of the cos- 

 mos, and for its every detail. The changes of an object are all pro- 

 duced by new arrangements of the matter constituting it, and by a 

 new distribution of the forces which belong to it. Their necessary- 

 direction is given in evolution in virtue of two principles, both of them 

 corollaries of the primary principle of the persistence of force : the 

 law of the instability of the homogeneous and the law of the multiplica- 

 tion of effects. 



Every body tends to pass into a more heterogeneous state, because 

 each of the units that constitute it is of necessity differently affected 

 from the others by the combined action of the others upon it ; because 

 the resulting difference places each unit in different relations with the 

 incident forces ; finally, because these units, owing to their respective 

 positions, cannot all receive the action of an external force in the same 

 direction and with the same intensity. This law, which accounts for 

 the commencement of the changes, accounts also for its continuance. 



At the same time a uniform external force, acting on a body, is 

 there dispersed; acting on unlike parts, it breaks up into forces differ- 

 ing in quality and intensity in proportion to the number and diversity 

 of these parts. The same is to be said of each fraction of the force ; 

 the process of dispersion goes on increasing, and the result is ex- 

 pressed by the law of the multiplication of effects. 



