172 A MODEL OF NATURE. 



of the association, have recently discussed the true meaning of our 

 scientific methods of interpretation; that Dr. James Ward has lately 

 delivered an attack of great power on matu' positions whicli eminent 

 scientific men have occupied; and that the approaching end of the 

 nineteenth century led Professor H»ckel to define in a more popular 

 manner his own ver}' definite views as to the solution of the "Rid- 

 dle of the Universe," are, perhaps, a sufficient justification of an 

 attempt to lay before you the difficulties which surround some of these 

 questions. 



To keep the discussion within reasonable limits, I shall illustrate the 

 principles under review b}^ means of the atomic theory, with compara- 

 tively little reference to the ether, and we may also at first confine our 

 attention to inanimate objects. 



THE CONSTRUCTION OF A MODEL OF NATURE. 



A natural philosopher, to use the old phrase, even if only possessed 

 of a most superficial knowledge, would attempt to bring some order 

 into the results of his observation of nature by grouping together 

 statements with regard to phenomena which are obviously related. 

 The aim of modern science goes far be3'ond this. It not only shows 

 that many phenomena are related which at first sight have little or 

 nothing in common, but, in so doing, also attempts to explain the 

 relationship. 



Without spending time on a discussion of the meaning of the word 

 "explanation." it is sufficient to say that our efforts to establish rela- 

 tionships between phenomena often take the form of attempting to 

 prove that if a liniited number of assumptions are granted as to the con- 

 stitution of matter, or as to the existence of quasi material entities, 

 such as caloric, electricity, and the ether, a wide range of observed facts 

 falls into order as a necessary consequence of the assumptions. The 

 question at issue is whether the hypotheses which are at the base of the 

 scientific theories now most generally accepted are to be regarded as 

 accurate descriptions of the constitution of the universe around us, or 

 merely as convenient fictions. 



Convenient fictions Ije it observed, for even if the}" are fictions they 

 are not useless. From the practical point of view it is a matter of 

 secondary importance whether our theories and assumptions are cor- 

 rect, if only the}' guide us to results which are in accord with facts. 

 The whole fabric of scientific theory may be regarded merel}' as a 

 gigantic ' ' aid to memory ; " as a means for producing apparent order 

 out of disorder by codifying the olxscrved facts and laws in accord- 

 ance with an artificial system, and thus arranging our knowledge under 

 a comparatively small number of heads. The simplification introduced 

 b)^ a scheme which, however imperfect it may be, enables us to argue 

 from a few first principles, makes theories of practical use. B3' means 



