144 INTRODUCTION TO SCIENCE 



the purely physical order: we almost always 

 know what to expect from a stone; it is among 

 the living that the unexpected happens. There 

 is absolute uniformity of response in the physical 

 order; there is caprice and humour in the ani- 

 mate order. We cannot recognize either individ- 

 uality or purposiveness in inanimate systems. 

 It is true that there is a great deal of effective 

 work done in the purely physical order. The sea 

 sculptures the shore, the river cuts a deep channel 

 in the rock, the glacier wears the mountains 

 smooth but what is done is mechanically deter- 

 mined by the external conditions, not by any 

 freely moving, purposive individuality. And 

 while inanimate objects have a certain power of 

 response to external stimuli, as the gunpowder 

 shows when a lighted match is applied to it, the 

 responses of a living creature in normal surround- 

 ings are of a higher order of efficiency, they make 

 for self-preservation and betterment. 



In discussing the characteristic features of living 

 creatures in the volume on EVOLUTION, we have 

 admitted that it is profitable to compare a living 

 creature to a machine and a fertile method of 

 discovery to press this comparison to its farthest. 

 "Yet the living organism differs from any machine 

 in its greater efficiency, and ... in being a self- 

 stoking, self-repairing, self-preservative, self-ad- 

 justing, self -increasing, self-reproducing engine! 



