DEMONSTRATION AND SELF-EVIDENCE 9 



Aristotle defines demonstration in terms of its final cause as a 

 syllogism productive of science. Then, using this definition of 

 demonstration itself as a principle of demonstration, he pro- 

 ceeds to demonstrate the definition of demonstration in terms 

 of its matter. He argues that if a syllogism is to produce the 

 kind of conclusion which is properly scientific it must proceed 

 from premises which are true, primary, immediate, better 

 known than, prior to, and cause of the conclusion. This is to 

 say that it must proceed from necessarily true, absolutely first 

 propositions, which look to no prior proposition for their evi- 

 dence but are calculated to supply evidence for other proposi- 

 tions. We speak of these propositions as self-evident. Scientific 

 knowledge is proven in a demonstration whose premises mani- 

 fest the truth of the scientific conclusion. As principles of the 

 conclusion these premises are properly premises. In any given 

 case, however, they may also be conclusions from other 

 premises. But it is impossible, of course, that every premise 

 be itself a conclusion from a prior premise. We must arrive 

 ultimately at premises which are only premises, at propositions 

 which are not shown to be evident by way of prior propositions 

 but whose evidence is found within themselves. These absolute 

 premises are ultimately the complex principles ^° of scientific 

 knowledge, themselves not properly scientific, but rather pre- 

 scientific. They are self-evident propositions, the propositions 

 spoken of in the Posterior Analytics as " the immediate basic 

 truths of syllogism " or, more determinately, of demonstration. 



immediately so (Ch. 3) . It is important to note that, for the most part, the sub- 

 sequent discussion of the requirements for demonstration is centered upon the 

 strictest type of propter quid demonstration and is only proportionally relevant to 

 other types. 



^° The absolute premises of demonstration are significant principles of demonstra- 

 tive discourse. So too is the middle term of the demonstration (which is not 

 identical with any premise, though it is built into each) . The former are complex 

 principles of demonstration. The latter is an incomplex principle. We are concerned 

 primarily with the complex principles of demonstration in this paper, although, as 

 we shall note, the definition itself plays a significant role in the discussion of these 

 complex principles. As a matter of fact Aristotle lists the definition as a type of 

 demonstrative principle in the very context of the discussion of immediate premises 

 (cf., St. Thomas' explanation for this, op. cit., lect. 5, n. 9) . 



