PART V. 



THE ATTAINMENT OF SCIENCE AND CERTITUDE. 



CHAPTER I. 

 SCIENCE AND DEMONSTRATION. 



248. ELEMENTARY NOTIONS DEFINED : TRUTH, IGNOR 

 ANCE, ERROR, EVIDENCE, CERTITUDE, OPINION, PROBA 

 BILITY, DOUBT. The terms &quot;true,&quot; and &quot;truth,&quot; are applied 

 to the things we know, to our knowledge of them, and to the 

 language in which we express this knowledge. Truth as applied 

 to things or reality, is called real or ontological truth. It is simply 

 the things, or reality, as revealed or manifested to some mind, and 

 thus related to that mind. It is identical with reality, and is the 

 proper object of metaphysics or ontology. The truth of lan 

 guage, called &quot;truthfulness,&quot; or &quot;veracity,&quot; is the conformity of 

 our language with our thought. It is ethical or moral in char 

 acter ; and the study of it belongs, therefore, to ethics or moral 

 philosophy. The truth of knowledge, called logical truth, is 

 the conformity of the mind judging about reality, or of the mind s 

 judgment about reality, with the reality to which the judgment 

 refers^ This knowledge and its truth are embodied in the mental 

 act of judgment. 



The term &quot; knowledge &quot; expresses that relation of the mind 

 to its object (things or reality), of which everyone is conscious, 

 but which is so simple, fundamental, primordial, that it does not 

 admit of definition proper, though it may be psychologically 



1 &quot; Veritas intellectus est adaequatio rei et intellectus secundum quod intellectus 

 dicit esse quod est, vel non esse quod non est.&quot; ST. THOMAS, Summa Contra 

 Gentes, i., q. 5. Cf. ST. THOMAS, In Met., iv., led. 8 : &quot; Verumenim est cum dicitur 

 esse quod est vel non esse quod non est. Falsum autem est cum dicitur non esse 

 quod est aut esse quod non est&quot; which reproduces Aristotle s definition : &quot; Tb /j.ty 

 yap \eyttv rb &/ /*rj !i/ai fj rb ^ by tlvai tyfvtios, rb Sf rb 6v tlvai Kai rb fj.^ t&amp;gt;v (ify flvai 

 a\i]dfs t &quot; Met. iii. 7, ed. Didot. Cf. MERCIER, Criteriologie, 5th edit. pp. 17-31 ; 

 SENTROUL, La verite et le progres du savoir, in the Revue neo-scolastique, May and 

 August, 1911. 



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