

On Some Processes of Scientific Reasoning. 23 



the eucalyptus vegetation, existed around us independent of 

 ourselves, we might mourn our fate. 



In conclusion, may we not say with some authority that 

 the evidence set forth in this paper on our own vegetation 

 is in favour of the eucalyptus being a fever-destroying tree ? 



Art. VIII. — On Some Processes of Scientific Reasoning. 

 By F. J. Piranl M.A., C.E. 



[Read October 12th, 1874.] 

 Mr. President and Gentlemen, — 



I have ventured this evening to offer a few remarks 

 on "Ideal Construction" and "The Introduction of Metem- 

 pirical Elements," processes of reasoning so named by 

 Mr. G. H. Lewes in a recent work,* the importance o± which 

 has been overlooked by most writers on Inductive Logic, 

 although it has been recognised by several Mathematicians 

 and Physicists. In the course of my remarks, I shall have 

 to briefly discuss the nature of some of the fundamental 

 ideas of Mechanics — a subject on the borderland between 

 Physics and Metaphysics, and one of great difficulty, if we 

 may judge by the controversies it has occasioned amongst 

 philosophers. But as science advances, it is well to examine 

 its foundations from time to time, so that we may ascertain 

 whether they are solidly built, and whether they are 

 capable of bearing the weight of the continually increasing 

 superstructure. 



The method of Ideal Construction may be thus de- 

 scribed : — The definitions and axioms of any branch of 

 science, or, at all events, of any branch of science which has 

 reached the Deductive stage, do not refer to the objects to 

 which the results of the science are eventually applied, 

 but to ideal conceptions of objects resembling the real ones, 

 but of a nature much simpler and more capable of mathe- 

 matical treatment. The conclusions arrived at by deductive 

 reasoning, absolutely true for the ideal objects, will only be 

 approximately true for the real ones, although sometimes 

 the degree of approximation will be such that our senses are 

 incapable of distinguishing it from absolute coincidence. 



* " Problems of Life and Mind," vol. i. 



