THE UNITY OF SCIENCE 11 



ferent things from falling apples, flying cannon-shot, rising 

 balloons; astronomy therefore came to be a science by itself. 

 But in essence — by which I mean, with respect to the laws and 

 principles of explanation which it employs — it is most of it 

 merely mechanics plus thermodynamics plus optics, while the 

 rest of it is chemistry. In other words, its fundamental con- 

 cepts and generalizations and its characteristic modes of rea- 

 soning, though not its instruments and methods of observa- 

 tion, are in the main the same as those of the science or group 

 of sciences commonly called physics. Thus, the conventional 

 distinction, though of great practical convenience, does not 

 correspond to any radical or real difference. Astronomy is 

 not a coordinate science with physics, in the sense in which 

 chemistry and biology may still plausibly be so regarded. So, 

 again, the sub-division of biology into botany and zoology is 

 not based either upon any absolutely sharp-cut contrast be- 

 tween the characteristics of the objects studied or upon any 

 essential distinctness in the laws or principles governing the 

 behavior of those objects. A division of all biology — i. e., of 

 the study of both plant and animal organisms — into morph- 

 ology, physiology and ecology — the study of organic form, of 

 organic functions or processess, and of the interaction be- 

 tween organism and environment — might conceivably be a 

 more serviceable, and it would not be a less clear and con- 

 sistent, one. 



It appears, then, that the now customary way of naming 

 and discriminating the individual sciences is more or less ac- 

 cidental and arbitrary. In order to discover their truly 

 significant relations we must look for some more fundamental 

 respects in which they are dissimilar. And there is, in fact, 

 one such dissimilarity which is so marked and important that 

 we may use it to sunder the sciences into two broad groups, 

 which may be called the Abstract Sciences, or Sciences of 

 Formal Relations, and the Concrete Sciences, or Sciences of 

 Phenomena. 



The Abstract Sciences consist chiefly of mathematics 



