224 THE SCIENCE OF LOGIC 



of logical questions&quot;. 1 Apart from the deeper philosophical as 

 pects of the problem, which belong rather to epistemology, there 

 is the purely logical aspect which arises from its bearings upon 

 logical method. And here, perhaps the principal difficulty in 

 treating it arises from the fact that the theory as to what con 

 stitutes the perfect form of knowledge or science has been worked 

 out from two distinct standpoints. Aristotle s conception of 

 science is built up from the standpoint of deduction, and worked 

 out in connexion with his doctrine on scientific Demonstration. 

 The modern conception of science is closely allied with induction, 

 and is set forth under the theory of Scientific Explanation. 

 These two views of the ideal of science are not mutually op 

 posed, but, when rightly understood, rather supplement each 

 other. We shall outline each of them successively, and endeavour 

 to compare them. 



About the reasoning processes which enter into all scientific 

 research, three distinct questions might be asked : (i) Are our 

 conclusions validly derived from our premisses ? (2) What sort 

 ought our premisses to be, if our knowledge is to be the most 

 perfect attainable? (3) By what sort of processes do we reach, 

 and establish or justify, the premisses we actually make use of? 

 Aristotle s three treatises on inference the Prior Analytics, the 

 Posterior Analytics, and the Topics are devoted to these three 

 questions respectively. The first examines the formal validity 

 of inference ; the second and third examine ,the conditions for its 

 truth. We argue sometimes from abstract, self-evident, necessary 

 principles ; sometimes from generalizations reached through ob 

 servation, induction, or authority not certain and necessary like 

 the former principles, but only contingent and probable. In 

 the Topics Aristotle dealt with these less perfect sources of 

 knowledge by &quot; analysing and formulating the actual procedure 

 of his contemporaries ; he did not, upon the whole, go ahead of 

 the science, the disputation, the rhetoric and the pleadings of his 

 day &quot;. 2 Roughly speaking, he covered the ground that would be 

 covered nowadays by the logic of induction and probability. The 

 knowledge which he conceived to be the ideal of perfect know 

 ledge was that derived by the syllogistic, synthetic method of 

 reasoning from necessary axioms like those of mathematics ; and 

 in the Posterior Analytics he inquired into the nature of demon- 



1 JOSEPH, op. dt., pp. 343, 349, 487. 2 ibid., p. 348. 



