I S73. ] Molecular Motion. 435 



term physical every form of energy which does not, like 

 chemistry, deal with the elementary substances ; for if this 

 were their meaning, it would simply be a truism to say that 

 all energy is either chemical or physical. By physical 

 energy they undoubtedly mean the ordinary and known 

 forms of energy manifested in the inorganic world, to which 

 we give the various specific names of attraction, repulsion, 

 light, heat, electricity, magnetism, and so forth. But here 

 we now approach the real question at issue, viz., are these 

 forms of energy along with chemical energy sufficient to 

 account for the phenomena of life and organic nature ? 



Chemistry and physics are insufficient, because they do 

 not account for the objective idea in nature. 



Whatever may be one's opinions regarding the doctrine 

 of final causes and the evidence of design in nature, all 

 must admit the existence of the objective idea in nature. 

 We see everywhere not only exquisite order and arrange- 

 ment in the structure of plants and animals, but a unity of. 

 plan pervading the whole. We see, in endless complexity, 

 beauty, and simplicity, the most perfect adaptation of means 

 to ends. The advocates of the physical theory are at least 

 bound to show how it is probable that this exquisite arrange- 

 ment and unity of plan could have been produced by means 

 of chemical and physical agencies. 



Natural selection never can explain the objective idea in 

 nature unless we suppose the selection to be made according 

 to a design or plan. Mr. Darwin has developed a new and 

 most important idea; but his theory can never, from its 

 very nature, explain the mystery of the organic world. 

 There must be a determining cause in the background of all 

 natural selection working out the objective idea. This I 

 trust will be rendered more evident when we come to con- 

 sider determination of motion in relation to final causes. 



Mr. Croll now considers the explanation of molecular 

 motion in regard to the form of objects. 



The objects of nature, as we have seen, are built up 

 molecule by molecule, and are thus the products of mole- 

 cular motion. Energy is that which moves or transports 

 the molecules in the building-up process ; but it is not the 

 mere transport of the molecules, as has been repeatedly 

 shown, which gives to the object produced its form. The 

 form assumed is due, not to the motion of the molecules, 

 but to the determination of that motion — to the way in 

 which the motions are guided and adjusted in relation to 

 one another. It is not the energy which conveys the bricks 

 that accounts for the form of the house, but that which 



