296 THE FOUNDATIONS OF ZOOLOGY 



do not know what the relation between mind and matter is, we 

 should like to find out, the controversies between the realists and 

 the idealists and the monists and the evolutionists and the materi- 

 alists will concern us as little as a summer shower concerns a 

 duck. 



Our knowledge of the stability of gravitation is accompanied 

 by an innate or natural tendency to respond to it as a stimulus, 

 a tendency which we share with most terrestrial animals and 

 plants, and all knowledge is no doubt accompanied by similar 

 emotional elements ; nor does it seem possible to discover any 

 sharp line between the responses which living things make by 

 nature and prior to experience and our own conscious, rational 

 adjustments; although the response of a germinating seed to 

 gravitation and our own acquaintance with Newton's laws are 

 things so different that it would do violence to the usage of com- 

 mon speech to call them both knowledge. 



If we analyze in the same way the scientific or objective value 

 of our confidence in the stability of the matter of the clock, of 

 the iron and the brass, and the wheels and bearings and pinions, 

 we find that this, like our confidence that its movements will be 

 orderly, is reasonable and judicious, but not necessary or absolute. 



We are led back, step by step, to the law of the indestructi- 

 bility of matter, just as we are led, by the study of gravitation 

 and similar phenomena, to the law of the conservation of energy ; 

 and finally we may perhaps be led to regard these laws as illus- 

 trations of a still more general mechanical principle, the continu- 

 ity of motion ; but those men of science who see most reason to 

 believe that all the phenomena of nature are phenomena of motion, 

 reducible to mechanical principles, are the ones who are most 

 emphatic in their assertion that, while it is folly to dispute these 

 principles, they know no evidence that they are necessary or 

 absolute. Our confidence in them is reasonable and judicious ; 

 but we know no reason why they must hold good. 



"All the phenomena in nature," says Berkeley, "are produced 

 by motion. Mechanical laws of nature or motion direct us how 

 to act, and teach us what to expect. Nor are we concerned at 

 all about the forces, neither can we know or measure them, 



