18 EDWARD D. SIMMONS 



IV. The Genesis of the Self-evident Proposition 



As St. Thomas teaches, the self-evident absolute premises 

 from which scientific conclusions are generated are natural to 

 the human intellect.-^ However, this does not mean, on the 

 one hand, that they are possessed from the very start as fully 

 formed conceptions dependent in no sense upon experience or, 

 on the other, that they are no more than mental constructs 

 fabricated by the intellect totally out of its own " stuff." In 

 the final lesson of his Commentary on the Posterior Analytics 

 St. Thomas finds fault with those who suggest that we already 

 possess the principles but do not know this from the beginning. 

 This is absurd since the principles of demonstration must be 

 better known than the conclusions they generate, and it is 

 impossible to know demonstratively and not be aware of this. 

 St. Thomas also disputes with those who say that self-evident 

 propositions arise in us from nothing. Experience indicates and 

 reason demands that they come from something. But they 

 cannot come from prior intellectual knowledge, for then they 

 would not be immediate. They are generated from previous 

 sense knowledge by way of an immediate induction."^ However, 

 to say this is not to imply that they are easily achieved. ^^ This 

 is simply not the case for the large majority of self-evident 



"'' Summa, I, q. 117, a. 1: " Inest enim unicuique horaini quoddam principium 

 scientiae, scilicet lumen intellectus agentis, per quod cognoscuntur statim a principio 

 naturaliter quaedam universalia principia omnium scientiarum." 



"® I say immediate induction to distinguish this from the mediate induction of a 

 conclusion whose evidence is supplied by a sufficient enumeration of singulars. 



^' Our students seem to be easily misled into identifying the self-evident with the 

 easily understood. This may be because in our classroom approach to them our 

 examples of the self-evident proposition are almost exclusively axioms which are 

 self-evident to all (e. g., The whole is greater than any one of its parts.) , or it may 

 be because of a tendency on the part of a student to give a psychologically sub- 

 jective reading to what must be understood objectively (i. e., to think " self- 

 evident " means evident to myself rather than in itself) . This confusion is not 

 limited to our students. For example, Joseph Brennan, in The Meaning of Phi- 

 losophy (New York: Harper and Bros., 1953) , p. 94, suggests two meanings to 

 " self-evident," namely, indemonstrable or completely clear to m,e. That the type- 

 writer I am using is gray is both indemonstrable and completely clear to me. But 

 it is in no sense self-evident. 



