236 THE SCIENCE OF LOGIC 



or &quot; exists,&quot; that a fact &quot; takes place,&quot; that an event &quot; happens,&quot; 

 is said indiscriminately to assert a &quot; truth &quot; or a &quot; fact &quot;. The ex 

 pressions &quot; That is zfact&quot; and &quot;That is true&quot; are synonymous. 

 Now, to give a causal demonstration (a demonstratio propter quid 

 Siori) of the truth of such an assertion is evidently the same as to 

 explain fully why and wherefore the thing or event or phenomenon 

 exists or takes place as it does to &quot; show &quot; or &quot; demonstrate &quot; it, 

 in and through its connexions with all its causes. 



Nevertheless, the term &quot;demonstration&quot; seems by preference 

 to be applied to the process by which we connect abstract truths 

 with their first principles; and &quot;explanation&quot; to the process by 

 which we connect the concrete existence and happening of things 

 and events with their causes, and so come to understand the modes 

 in which, or the laws according to which, they are produced by 

 those causes. We may know that the three angles of a triangle 

 are equal to two right angles without knowing why ; and we may 

 know that ice begins to form on the surface of a pond and not at 

 the bottom, without knowing why. To answer the first &quot;why &quot; is 

 to demonstrate a theorem in geometry ; to answer the second is 

 to explain a phenomenon in physics. To demonstrate truths is 

 simply to show their connexion with simpler truths which we 

 already understand, and ultimately with first principles : to show 

 how they are involved in the latter, to harmonize and fit them in 

 with that part of our knowledge to which they are logically or 

 rationally akin. To explain facts is simply to show why they 

 happen, how they occur, how they are connected with their causes, 

 what these causes are, and what are the laws according to which 

 they bring those facts about. We demonstrate consequent by 

 antecedent until we reach first principles ; we explain effects by 

 causes until we reach remote causes, and, ultimately, the One, Un 

 created First Cause. 



It is in this discovery of causes, and of the laws to which 

 their activities conform, that scientific explanation essentially 

 consists. We &quot; explain &quot; a fact or phenomenon when we show 

 it to be an instance of the application of some law. But this 

 &quot; law &quot; itself may be only a general statement of the uniform 

 occurrence of the fact in certain definite circumstances (247) ; 

 and if so, the &quot; law &quot; itself needs explanation, suggesting as it does 

 a distinct &quot; why ? &quot; of its own. And so we try to explain the law 

 itself in turn. This we do either (i) by showing that it expresses 

 the combined application, simultaneous or successive, of certain 



