14 EDWARD D, SIMMONS 



tions self-evident (consider the examples given above for the 

 factually evident proposition) . Certainly true propositions in 

 contingent matter are indemonstrable because of a deficiency 

 in matter. Self-evident propositions are always in necessary 

 matter, and their indemonstrability springs from their excel- 

 lence rather than from some deficiency in matter. Demonstra- 

 tion makes evident something which is not already evident. 

 To be demonstrable entails a privation. Because they are 

 evident in themselves, self-evident propositions do not have 

 this privation.^^ 



Self-evident propositions are necessarily true and immediate. 

 This makes them at once primary: they have no propositions 

 prior to them (upon which they depend for evidence) , and 

 they are presupposed to the mediate propositions which look to 

 them for evidence. Insofar as they supply evidence for these 

 mediate propositions they cause them to be conclusions. And 

 they can be related to the conclusion as cause to effect only 

 insofar as they are prior to and better known than the conclu- 

 sion. The " basic truths of syllogism " are basic insofar as they 

 admit of no prior propositions necessary to make them evident. 

 They are truths of the syllogism insofar as they are principles 

 from which conclusions can be generated. 



III. The Types of Self-evident Proposition 



We have noted that a self-evident proposition is one which 

 is known to be necessarily true once its terms are understood. 

 The most perfect instance of this is found in the proposition 

 in which the predicate is of the definition of the subject.^^ Once 



^* Though scientific or demonstrated knowledge is spoken of as perfect knowledge 

 (cf., In I Post. Anal., led. 4, n. 5) , it is clear that it is inferior to the pre-scientific 

 absolute premises of demonstration. 



^* Summa, I, q. 17, a. 3 ad 2: " Nam principia per se nota sunt ilia quae statim 

 intellectis terminis cognoscuntur ex eo quod praedicatum ponitur in definitione 

 subiecti." As Cajetan points out in his Commentary on the Posterior Analytics 

 (Book I, Ch. 19) , St. Thomas does not intend in texts such as this one strictly 

 to define the self-evident proposition but to manifest the principal case. An 

 example of a self-evident proposition which does not have its predicate within the 

 definition of its subject is Every rational animal is capable of speech. 



