MULTIPLICATION OF EFFECTS. 415 



most complex in structure of all substances, and possesses 

 the most complex functions ; it also readily decomposes. 

 In consequence of the complexity of the molecular consti- 

 tution of matter and of the extremely crude ways in which 

 we commonly apply the physical forces to it, the usual 

 result of the action of a cause is to produce a multiplicity 

 and variety of effects. One physical change in a body 

 rarely happens alone, others occur with it ; for instance, 

 when iron is cooled from a red heat it suffers numerous 

 changes. 1 Multiplication of effects, with the consequent 

 introduction of differences, is the great process by means of 

 which the forces of nature produce diversity of phenomena 

 throughout the universe. An uniform cause sometimes 

 produces a variable or a differentiated effect, in conse- 

 quence of variation or difference of resistance (resistance 

 itself being a condition). Simultaneously with this pro- 

 cess of differentiation there is continually occurring an 

 opposite action of concurrent or compound forces, in which 

 of a number of causes, each contributes a part towards pro- 

 ducing a single result, and simplicity is converted into 

 complexity by means of combination and permutation of 

 causes. For instance, a number of influences concur to 

 restore an invalid to health ; a multitude of streams act 

 as a compound cause to fill the ocean ; and so on. And 

 these two opposite processes of divergence and convergence 

 of causes operate throughout nature in nearly equal 

 amount. In some cases each cause produces its effect 

 independently of the others, but in other cases all the 

 other causes must conspire to act with it, otherwise no 

 effect is produced. 2 



1 See Chapter IV. p. 33. 



2 The subjects of instability of phenomena, multiplication of effects, 

 differentiation, integration, and equilibration of phenomena, evolution, 



