A Rational and Humane Science 



poor little Man who, having noted the stars for 

 a few centuries, is so sure that he understands 

 their movements, and that he is versed in all the 

 " ordinances of heaven." 



Thus it would appear that every Nature-problem 

 is so enormously complex that it can only be got at 

 by what we have called the Method of Ignorance. 

 Let us take a practical Science problem like that 

 of Vaccination. The question here, put in its 

 simplest terms, seems to be. Whether Vaccination, 

 with calf or human lymph, prevents or alleviates 

 Smallpox ; and if it does, whether it does so without 

 engendering other evils at least as great. At 

 first sight this may appear to you a very simple 

 question, and easy to solve ; but the moment you 

 come to think about it, you see its extreme com- 

 plexity. In the first place, it is obvious that in 

 a question like this, individual cases afford no 

 test. It is obvious that the fact that A. is vacci^ 

 nated and has not taken small-pox proves nothing, 

 for there is nothing to show that he would have 

 taken it if he had not been vaccinated. And 

 when you have got people vaccinated by the hundred 

 and the thousand, you still are not certain ; for 

 these people may belong to a certain class, or a 

 certain locality, or may have certain habits and 

 conditions of life, which may account for their 

 comparative immunity, and these causes must 

 be eliminated before any definite conclusion can 

 be reached. Thus it is not till the great mass 

 of the population is vaccinated that we can expect 

 reliable statistics. But the introduction of a praq^ 



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