2 Elementary Biology. 



relationships were themselves found to have a genetic con- 

 nection. Natural laws were found to be capable of being 

 systematised into bodies of truth, or departments of science, 

 more commonly, but with less accuracy, termed sciences. 



One step alone remained in this process of unification 

 of knowledge, namely, the determination of the inter- rela- 

 tionships of the various departments of science. Hence 

 arose the various attempts which have been made within 

 comparatively recent years to formulate a classification of 

 the sciences. It can scarcely be said that a uniform agree- 

 ment has been come to as yet upon all points with reference 

 to that classification, but the general order of relationship 

 and development of the several sciences may be said to be 

 now beyond controversy. 



A careful distinction must be drawn at the very outset 

 between what constitutes the subject-matter of the sciences 

 themselves, and the methods or instruments which are em- 

 ployed in their study. These methods are two in number, 

 and entirely different in their nature qualitative, em- 

 bracing the methods of inductive and deductive Logic, 

 and quantitative, or mathematical, embracing that section 

 of mathematics usually known as Pure Mathematics. 



All scientific knowledge rests fundamentally on the belief 

 in the ' order of nature ; ' that is to say, on the belief that 

 under the same conditions the same cause will produce 

 the same effect. The basis for this belief is the universal 

 experience of mankind, obtained by observation of and 

 experiment on natural phenomena, and formulated there- 

 from by inductive reasoning, the induction going by the 

 name of the law of causality. 



In attempting to classify or arrange the sciences in their 

 natural order, regard must be had to the several conditions 

 of a natural classification. 



Firstly, the sciences must be arranged in the order of 

 their complexity ; that is to say, sciences which involve 

 simple and definite generalisations must precede sciences 



