198 THE LESSON OF EVOLUTION 



The difference between the two methods is that, 

 whereas speculation starts a chain of reasoning from 

 one or two propositions which are taken as absolutely 

 true, science reasons from the basis of as large a 

 number of observations as possible, and tries to find 

 an hypothesis which connects them all together, or 

 explains them, as it is usually called. 



Evidently this scientific process is a very laborious 

 one, but it is more to be trusted than speculation. 

 For we can never be certain that any single propo- 

 sition is quite true, or that it contains the whole 

 truth ; and, as it is impossible to allow for modifying 

 circumstances, reasoning alone may lead us far 

 astray ; while, with the scientific method, attention 

 is directed to errors of observation, which can be 

 corrected ; and new facts are constantly confronting 

 us which tend to prove, or to disprove, or to modify 

 our theories. These theories, in time, get estab- 

 lished as what we call "laws of nature;" that is, 

 accurate records of observed cause and effect ; and 

 they thus form a touchstone of exact knowledge, by 

 which the speculative philosophies must be tried. 



No doubt these two processes of observation and 

 speculation went on in a desultory, impulsive man- 

 ner for several thousands of years, during which 

 man not only learnt a great deal about the material 

 world, but was led to speculate about the immaterial . 

 or spiritual world, which he believed to encompass 

 him on all sides. We can never know with certainty 

 how the conception of an invisible, spiritual world 

 arose in the human mind ; but we know, as a matter 

 of fact, that it did do so at an early stage of the 



