226 POPULAR SCIENCE MONTHLY, 



be combined or physical chemistry interpolated between physics and 

 chemistry. Similarly anthropology might be placed between phys- 

 iology and psychology while the first four sciences might be combined 

 as mathematics. How this subdivision is to be carried out is purely 

 a practical question which will be answered differently by different ages 

 and concerning which it is useless to quarrel. 



I would like, however, to call attention to the three great divisions : 

 Mathematics, energetics and biology (in the broader sense). They 

 represent the three guiding thoughts which up to the present mankind 

 has brought forth for the purpose of mastering scientifically its ex- 

 periences. Order is the fundamental thought of mathematics, energy 

 the guiding concept from mechanics to chemistry; for the last three 

 sciences it is life. Mathematics, energetics and biology therefore em- 

 brace the whole body of the sciences, while logic precedes them all. 



Before entering upon a more detailed consideration of these sci- 

 ences, it is well to anticipate an objection which may be raised on the 

 basis of the following fact. There are in addition to the previously 

 mentioned sciences (as well as the intermediate ones) many others such 

 as geology, history, medicine, philology, which present difficulties if 

 a place is sought for them in our scheme, and which, nevertheless, 

 demand consideration. It is often characteristic of them that they 

 bear relation to several of the sciences which have been enumerated; 

 and still more characteristic of them is it that they do not search for 

 universal relations as do the pure sciences, but rather treat existing 

 complex objects in order to ' explain ' or discover their origin, extent, 

 distribution, in a word their time and space relations. To accomplish 

 this object they make use of the relations which the pure sciences have 

 put at their disposal. It is best to designate these sciences as applied 

 sciences. This term is not meant to imply either exclusively or even 

 chiefly technical application. It is merely intended to express the 

 fact that here interrelations of the parts of a ready-made object are 

 rendered intelligible by the application of the general laws which have 

 been discovered by pure science. 



In a problem of this nature it is usually necessary to make use of 

 several different pure sciences simultaneously for an explanation, be- 

 cause the abstract method of the pure sciences is not permissible here. 

 To omit certain parts and to limit oneself to certain others is from 

 the very nature of the problem out of the question. Astronomy is an 

 applied science of this sort. It is based immediately upon mechanics; 

 in its instrumental part upon optics; while in its contemporaneous 

 spectroscopic development it borrows much from chemistry. Thus his- 

 tory is applied sociology and psychology; medicine makes use of all 

 preceding sciences up to psychology, etc. 



It is important to realize the nature of these applied sciences since 



