A MODEL OF NATURE. 189 



the simplest phenomena as irreconcilable and unintelligible, in spite 

 of the fact that means of reconciling them are known to everybody, 

 in spite of the fact that the reconciling theory gives a general correla- 

 tion of an enormous number of phenomena in every branch of science, 

 and that the outstanding difficulties are connected not so much with 

 the fundamental hypotheses that matter is composed of distinguishable 

 entities which are capable of separate motions as with the much more 

 difficult problem of what these entities are. 



On these grounds the physicist may believe that, though he can not 

 handle or see them, the atoms and molecules are as real as the ice 

 crystals in a cirrus cloud which he can not reach; as real as the unseen 

 members of a meteoric swarm whose death glow is lost in the sunshine, 

 or which sweep past us, unentangled, in the night. 



If the confidence that his methods are weapons with which he can 

 fight his way to the truth were taken from the scientific explorer, the 

 paralysis which overcomes those who believe that they are engaged in 

 a hopeless task would fall upon him. 



Physiology has specially flourished since physiologists have believed 

 that it is possible to master the physics and chemistry of the framework 

 of living things, and since they have abandoned the attitude of those 

 who placed in the foreground the doctrine of the vital force. To sup- 

 porters of that doctrine the principle of life was not a hidden directing 

 power which could perhaps whisper an order that the flood gates of 

 reservoirs of energy should now be opened and now closed, and could, 

 at the most, work only under immutable conditions to which the living 

 and the dead must alike submit. On the contrary, their vital force 

 pervaded the organism in all its parts. It was an active and energetic 

 opponent of the laws of physics and chemistry. It maintained its own 

 existence not by obeying but by defying them; and though destined 

 to be finally overcome in the separate campaigns of which each indi- 

 vidual living creature is the scene, yet, like some guerrilla chieftain, it 

 was defeated here only to reappear there with unabated confidence 

 and apparently undiminished force. 



This attitude of mind checked the advance of knowledge. Difficulty 

 could be evaded by a verbal formula of explanation which in fact 

 explained nothing. If the mechanical, or physical, or chemical causes 

 of a phenomenon did not lie obviously upon the surface, the investi- 

 gator was tempted to forego the toil of searching for them below; it 

 was easier to say that the vital force was the cause of the discrepancy, 

 and that it was hopeless to attempt to account for the action of a 

 principle which was incomprehensible in its nature. 



For the physicist the danger is no less serious, though it lies in a 

 somewhat different direction. At present he is checked in his theories 

 by the necessity of making them agree with a comparatively small 

 number of fundamental hypotheses. If this check were removed his 

 fancy might run riot in the wildest speculations, which would be held 



