84 PRESENT-DAY RATIONALISM 



physics ? The advocates of the physical theory must afford 

 us some explanation of the cause of the determination of 

 molecular motion derived from physics and chemistry, if 

 their theory in reality rests upon a true foundation. 



" The chief argument in favour of this theory seems 

 to be that a// the energies in Nature to which the term 

 ' vital ' can be applied evidently have a chemical or 

 physical origin. For example, the vital energies of our 

 bodies are derived from the food we eat, the water we 

 drink and the air we breathe ; they, therefore existed 

 first under the form of chemical affinities. The same is 

 the case in regard to plants ; all the energies in operation 

 in the plant are in like manner derived from the nutri- 

 ment received through its leaves and rootlets. But the 

 energy is no longer chemical or physical after it has 

 changed its mode of operation. If energies are to bear 

 names according to their mode of operation (which is the 

 practice in science), then energies differing from those 

 of chemistry and physics must have a name by which 

 they are to be distinguished. Why then, not call them 

 ' vital energies ' ? 



" The terms light, heat, electricity, magnetism, etc., 

 are diff"erent names which we apply to different modes of 

 molecular motion ; and it is true that at present little is 

 known regarding the nature of their modes of motion ; 

 but notwithstanding this we have reason to conclude that, 

 although we knew all that absolutely can be known re- 

 garding them, yet zV ivould not afford us any explanation 

 of the cause of the determination of molecular motion in 

 organic nature. 



" If one plant or animal differs from another, or the 

 parent from the child, it is because in the building-up 

 process the determinations of molecular motion were 

 different in the two cases ; and the true and fundamental 



