INTROD UCTOR Y REMARKS. 5 



the errors both of a priori reasoning and of commentators, 

 and, at all events, prevents their becoming cumulative ; 

 though the theories or explanations of a fact be different, the 

 fact remains the same. It is, moreover, itself the exponent of 

 its discoverer's thought : the observation of known pheno- 

 mena has led him to elicit from nature the new phenomenon : 

 and though he may be wrong in his deductions from this after 

 its discovery, the reasonings which conducted him to it are 

 themselves valuable, and having led from known to unknown 

 truths, can seldom be uninstructive. 



Very different views existed amongst the ancients as to 

 the aims to be pursued by physical investigation, and as to 

 the objects likely to be attained by it. I do not here mean 

 the moral objects, such as the attainment of the summum bo- 

 num, &c., but the acquisitions in knowledge which such 

 investigations were likely to confer. Utility was one object 

 in view, and this was to some extent attained by the progress 

 made in astronomy and mechanics. Archimedes, for instance, 

 seems to have constantly had this end in view ; but, while 

 pursuing . natural knowledge for the sake of knowledge, and 

 the power which it brings with it, the greater number seemed 

 to entertain an expectation of arriving at some ultimate goal, 

 some point of knowledge, which would give them a mastery 

 over the mysteries of nature, and would enable them to ascer- 

 tain what was the most intimate structure of matter, and the 

 causes of the changes it exhibits. Where they could not dis- 

 cover, they speculated. Leucippus, Democritus, and others 

 have given us their notions of the ultimate atoms of which 

 matter was formed, and of the modus agendi of nature in 

 the various transformations which matter undergoes. 



The expectation of arriving at ultimate causes or essences 

 continued long after the speculations of the ancients had been 

 abandoned, and continues even to the present day to be a 

 very general notion of the objects to be ultimately attained 

 by physical science. Francis Bacon, the great remodeller of 

 science, entertained this notion, and thought that, by experi- 

 mentally testing natural phenomena, we should be enabled 

 to trace them to certain primary essences or causes whence 

 the various phenomena flow. These he speaks of under the 



