16 HISTORY OF INDUCTIVE SCIENCES. 



real science, the conjunction of clear ideas with dis- 

 tinct facts, was interrupted; and, in such cases, men 

 dealt with ideas alone. They employed themselves 

 in reasoning from principles, and they arranged, 

 and classified, and analyzed their ideas, so as to 

 make their reasonings satisfy the requisitions of 

 our rational faculties. This process of drawing 

 conclusions from our principles, by rigorous and 

 unimpeachable trains of demonstration, is termed 

 Deduction. In its due place, it is a highly import- 

 ant part of every science ; but it has no value when 

 the fundamental principles, on which the whole of 

 the demonstration rests, have not first been obtain- 

 ed by the induction of facts, so as to supply the 

 materials of substantial truth. Without such ma- 

 terials, a series of demonstrations resembles physi- 

 cal science only as a shadow resembles a real object. 

 To give a real significance to our propositions, In- 

 duction must provide what Deduction cannot sup- 

 ply. From a pictured hook we can hang only a 

 pictured chain. 



Distinction of common Notions and Scientific 

 Ideas. When the notions with which men are 

 conversant in the common course of practical life, 

 which give meaning to their familiar language, and 

 employment to their hourly thoughts, are compared 

 with the Ideas on which exact science is founded, 

 we find that the two classes of intellectual opera- 

 tions have much that is common and much that is 

 different. Without here attempting fully to explain 



