SCIENCE AND DEMONSTRATION 215 



judgments established by induction about the facts of sense is 

 a source of physical certitude, (c] The testimony of our fellow- 

 men is, under certain conditions, a source of moral certitude. But 

 evidence from all three sources combines and coalesces in the 

 production of the greater part of the certain knowledge which is 

 actually possessed by men generally. 



The main characteristic of pure metaphysical certitude is this, 

 that it is for the most part 1 confined to truths of the abstract 

 order, to judgments about possible essences or objects of thought, 

 judgments which abstract from the question of the existence or 

 non-existence, occurrence or non-occurrence, of these objects in 

 the sphere of actual reality. In other words, it concerns judg 

 ments, whether affirmative or negative, in materia necessaria (85-8) ; 

 or again, judgments which affirm a necessary identity or a necessary 

 incompatibility between the objective concepts compared ; that is 

 to say, judgments which have been described as apodeictic (89-90). 

 And all such judgments, dealing as they do with the necessary 

 implications of concepts, are the intellectual expressions of taws, 

 and are, therefore, universal judgments at least potentially uni 

 versal. 2 All the truths of pure mathematics are of this order. 

 The evidence is intrinsic to the truths themselves ; and it is 

 cogent, whether it be immediate evidence of axioms, or mediate 

 evidence of conclusions deduced logically from such axioms. 



Physical certitude is, first of all, the certitude we may have 

 about the actual existence or occurrence of concrete facts of our 

 own individual sense experience. These all occur in time and 

 space. For present facts of actual sense experience we rely on 

 the testimony of our senses ; for certitude about past facts of our 

 own individual experience we must rely on memory. But, 



1 Except where the concept of the subject involves in it the concept of actual 

 existence. &quot; We have an example of existence being involved in the idea when we 

 mentally or orally affirm I exist . I cannot even think I without implicitly 

 affirming that I exist ; the very fact of saying to myself I is an acknowledgment 

 that I exist, for I cannot think I without existing and being conscious of my 

 existence. Hence to say I do not exist is to be involved in a concrete contradic 

 tion, just as to say Two and two do not make four is to be involved in an abstract 

 contradiction ; it is to deny in the predicate what is implicitly affirmed in the 

 subject. . . . Hence it is that we are each of us metaphysically certain of our own 

 existence, and the causal proof of the Being of a God which is based upon our 

 personal existence leads to metaphysical certitude that God exists.&quot; TOOHEY, ibid., 

 pp. 255-6. 



2 Their actual extension may include only a single subject, as, for example, 

 when such judgments are formed about the thinking subject himself, or about God, 

 the Necessary Being. 



