CONCEPTS OF &quot; REASON &quot; AND &quot; CA USE &quot; 65 



not merely its efficient cause or causes, but its inner nature, its 

 formal and material causes. But its specific nature, or formal 

 cause, is revealed by its sensible energies and properties : it is only 

 by studying these which are nearer and more familiar to us, 

 whose knowledge comes through the senses that we can know 

 that which is more remote from us, though prior and simpler in 

 itself, viz. the specific nature, the ground of the universal law. 

 The principle underlying this progress of thought is expressed in 

 the Scholastic aphorism : Operari sequitur esse, or, Qua/is est 

 operatic , talis est natura : As a thing is so it acts: Action is the 

 index of essence. And a knowledge of the formal cause or specific 

 nature of a thing helps to bring to light its purpose or function in 

 the universe, i.e. its final cause, the reason why it exists and acts, 

 the design it accomplishes in nature. Without a knowledge of the 

 &quot; why and wherefore &quot; of a thing, our knowledge of it is incomplete. 



When, for example, Pasteur s experiments demonstrated that fermentation 

 is due to the action of a living microbe, or that every living cell has its origin 

 from some other living Cell, he discovered in the microbe the efficient cause 

 of fermentation, in the parent-cell the efficient cause of the younger cell. 



Again, the chemical elements combine to form compounds in certain 

 definite proportions by weight. The components, hydrogen and chlorine, enter 

 into the formation of hydrochloric acid in the proportion of i part of hydrogen 

 t 35-5 parts of chlorine by weight. Those definite quantities are material 

 causes of the various combinations into which these elements enter, for the 

 material mass or quantity is independent of specific change, i.e. change of 

 substance or substantial &quot; form,&quot; and attaches to the material cause or prin 

 ciple in corporeal substances and agents. 



Again, the combination of hydrogen and chlorine to form hydrochloric 

 acid is seen to depend on the chemical affinities of the two reacting bodies for 

 each other. These affinities being themselves specific properties of the 

 respective components, the formation of the acid is the result of the specific 

 natures of these components. But the specific nature and the specific pro 

 perties of a body depend on, and are determined by, its specific, essential or 

 substantial &quot;form&quot;: its &quot; formal&quot; cause. So that when we determine the 

 law of a chemical combination, i.e. the fixed, uniform mode of action of the 

 substances involved elements or compounds, we are bringing to light the 

 formal causes, the specific constituent principles, the specific natures, of 

 those substances. 



Again, the peculiar affinities of the chemical elements determine the 

 combinations which their respective natures incline them to realize. Hence, 

 to detect the affinities of these elements, and to characterize the latter by 

 those affinities, is to discover the innate tendencies which incline these 

 elements to form certain combinations. In other words, it is to discover the 

 internal purpose of the reacting bodies. The establishment of the laws of a 

 chemical combination is, therefore, the discovery not merely of the formal, but 

 VOL. II. 5 



