SCIENCE AND DEMONSTRATION 235 



are made &quot; l the supreme truth of God s existence, which is the 

 goal of all philosophy. Mixed proof, in this application of it, 

 whereby we ascend from the knowledge of effects to the knowledge 

 that there must exist a cause adequate to account for them, is 

 obviously a posteriori. It is not to be confounded with ordinary 

 scientific induction, which gives us physical certitude about the laws 

 of created causes (229-33); for, based as it is on the principle of 

 causality and the immediate data of consciousness (249), it gives 

 us metaphysical certitude of the existence of a First Cause. 



(d] Circular or Regressive Demonstration. Reason ascends 

 (by induction, or by a posteriori demonstration) from effect to 

 cause, and then descends again to explain the former by the 

 latter. Its movement is first analytic, then synthetic (202). It 

 thus completes a sort of circle or regress, returning in a certain 

 sense to its starting-point. Such a complete process is called 

 circular or regressive reasoning. This is the natural path of valid 

 thought in the discovery and proof of truth. Hence it must not 

 be confounded with the fallacy known as the vicious circle (the 

 circulus vitiosus or petitio principii). The latter is an attempt to 

 prove a premiss by means of the conclusion which that very pre 

 miss is employed to establish 2 (198). But regressive demonstra 

 tion sets out inductively from some fact or phenomenon, whose 

 existence is certain, though its nature or cause is only vaguely con 

 jectured as an hypothesis ; and it returns from that nature or cause 

 to the existing fact, only when it has established the former, and 

 reached such a knowledge of it as explains the fact or phenomenon 

 in question. 



255. DEMONSTRATION AND SCIENTIFIC EXPLANATION. 

 &quot; POPULAR EXPLANATION &quot;.What strict Aristotelean demon 

 stration is to the deductive sciences, that scientific explanation is 

 to the inductive sciences. We are said rather to demonstrate a 

 &quot;truth&quot; and to explain a &quot;fact,&quot; but the difference is only a 

 verbal one. A &quot; truth &quot; is a judgment that is in conformity with 

 some reality which it purports to interpret ; the judgment itself 

 is the logical truth, the reality is the ontological truth. The reality 

 itself has various names: &quot;being,&quot; &quot;thing,&quot; &quot;event,&quot; &quot;fact,&quot; 

 &quot; phenomenon &quot;. The judgment which asserts that a thing &quot; is &quot; 



1 Rom. i. 20. 



2 The premisses of a valid demonstration must be known otherwise than through 

 a knowledge of the conclusion itself; they must be known from an independent 

 source. 



