BIOLOGY AN INDUCTIVE SCIENCE. I05 



The Doctrine of Descent is really nothing but a great in- 

 ductive law, to which we are led by grouping and compar- 

 ing the most important empirical laws of Morphology and 

 Physiology. We are obliged to draw our conclusions 

 according to the laws of induction in every case in which 

 we are unable to establish the truths of nature immediately 

 by the infallible method of direct measurement, or mathe- 

 matical calculation. In the study of animated nature, we 

 are seldom able entirely to ascertain the significance of 

 phenomena immediately, and by infallible mathematical 

 means, as is possible in the much simpler study of inorganic 

 bodies, in Chemistry, Physics, Mineralogy, and Astronomy. 

 In the last especially, we can always employ the very 

 simple and absolutely sure method of mathematical calcula- 

 tion. But in Biology, this is for many reasons entirely 

 impossible, and especially because the phenomena in it are 

 far too complex to admit of immediate solution by mathe- 

 matical analysis. We are therefore compelled to proceed 

 inductively ; in other words, from the mass of separate 

 observation we must gradually draw general conclusions, 

 which must be more and more approximately correct. 

 These inductive conclusions, it is true, cannot claim the 

 absolute certainty of mathematical propositions ; but they 

 are more and more approximately true in proportion with 

 the increase in extent of the experiences on which they are 

 based. The importance of such inductive laws is in no way 

 lessened by the circumstance that they must only be 

 regarded as provisional scientific achievements, w~hich may 

 possibly be improved, or perfected, by the further progress 

 of knowledge. This is equally true of the greater part of 

 knowledge in other sciences ; for example, in Geology and 



