i&B HELMHOLTZ 



individuals and peoples is also in conformity with law, 

 as is the object of philosophical, philological, historical, mor- 

 al, and social sciences to establish. But in mental life, the 

 influences are so interwoven, that any definite sequence can 

 but seldom be demonstrated. In Nature the converse is the 

 case. It has been possible to discover the law of the origin 

 and progress of many enormously extended series of natural 

 phenomena with such accuracy and completeness that we 

 can predict their future occurrence with the greatest cer- 

 tainty; or in cases in which we have power over the con- 

 ditions under which they occur, we can direct them just 

 according to our will. The greatest of all instances of 

 what the human mind can effect by means of a well-recog- 

 nised law of natural phenomena is that afforded by modern 

 astronomy. The one simple law of gravitation regulates the 

 motions of the heavenly bodies not only of our own planetary 

 system, but also of the far more distant double stars; from 

 which, even the ray of light, the quickest of all messengers, 

 needs years to reach our eye; and, just on account of this 

 simple conformity with law, the motions of the bodies in 

 question can be accurately predicted and determined both 

 for the past and for future years and centuries to a fraction 

 of a minute. 



On this exact conformity with law depends also the 

 certainty with which we know how to tame the impetuous 

 force of steam, and to make it the obedient servant of our 

 wants. On this conformity depends, moreover, the intellectual 

 fascination which chains the physicist to his subjects. It is 

 an interest of quite a different kind to that which mental 

 and moral sciences afford. In the latter it is man in the 

 various phases of his intellectual activity who chains us. 

 Every great deed of which history tells us, every mighty 

 passion which art can represent, every picture of manners, 

 of civic arrangements, of the culture of peoples of distant 

 lands or of remote times, seizes and interests us, even if 

 there is no exact scientific connection among them. We 

 continually find points of contact and comparison in our 

 conceptions and feelings; we get to know the hidden capac- 

 ities and desires of the mind, which in the ordinary peace- 

 ful course of civilised life remain unawakened. 



