2 THE SCIENCE OF LOGIC 



In all logical inference, our reason for assenting to the conclusion 

 is its evident connexion with premisses to which we have already 

 assented. But how do we come to assent to these latter ? Either 

 because they are self-evident like the universal axioms involved 

 in all inference (193), or derived by demonstrative evidence from 

 such self-evident truths, or generalized by induction from observed 

 facts. The general truths of the sciences may, then, be roughly 

 divided into these three classes : (a) self-evident axioms or 

 principles, such, for example, as &quot; The whole is greater than its 

 part &quot; : these are reached by a comparatively simple process of 

 intellectual abstraction and intuition, involving Definition and 

 Division of concepts, and their mutual comparison in judgment ; 

 () general truths that are not self-evident, but which have been 

 generalized by Induction from observed facts ; (c) conclusions 

 inferred by Demonstration from truths of classes (a) or (). 



Before the inductive method was developed, attention was largely de 

 voted, in the traditional Aristotelean logic, to definition, division, and 

 demonstration the tres modi sciendi as they were called. 1 Definition, by 

 analysing our concepts of things into the simplest possible notions, gives rise 

 to certain primordial, self-evident relations between these notions. These 

 relations are formulated in judgments and propositions which furnish the 

 foundations of the scientific edifice the principles of the sciences. While 

 definition thus analyses our concepts, and gives us information about the 

 nature of their objects, it thereby also shows us wherein those objects agree 

 in thought and wherein they differ from one another. The process of 

 differentiation, or classification, or division, is thus the indispensable con 

 comitant of definition. 



According as the mind becomes equipped with its elementary ideas and 

 judgments by means of sense observation, and intellectual abstraction and 

 intuition, it has recourse to the third mode of procedure, demonstration : 

 it draws certain and evident conclusions from self-evident principles, and from 

 these conclusions still further conclusions, and so on. The employment of 

 those various functions or factors of science, for the advance of knowledge, 

 is what the Scholastics called METHOD. 



The process of (real) definition, understood in the Scholastic sense as an 

 explanation of the nature of a thing, and the concomitant process of (real) 

 division or classification, were always regarded in Aristotelean philosophy as 

 material processes, involving observation and analysis of facts, abstraction, 

 generalization, comparison, and even inference and verification of hypotheses 

 in a word, all the processes nowadays described as &quot; subsidiary to in 

 duction &quot;. These made up the analytic stage of the Scholastic method, as 

 demonstration constituted its synthetic stage. 



20 1. LOGIC AND METHOD. Before investigating the method 



1 Cf. ZIGLIARA, Logica, (13), (44). 



