172 WHAT IS SCIENCE? 



though we may neglect that possibility for our purpose. 

 A more serious possibility would remain, namely, that 

 we had misinterpreted their information, and this is 

 actually the greatest danger in knowledge acquired at 

 second-hand. Thus the error about the length of the walk 

 quoted just now, doubtless arose from the fact that the 

 original Sunday walk was eight miles, and that a weaker 

 generation had abbreviated it to six. However, there 

 are other sources of error ; people do draw false conclu- 

 sions directly from experience ; and even if we could 

 be sure that we had rightly understood an honest 

 informant, there would still be a danger that his informa- 

 tion was wrong. In discussing these other sources 

 and giving examples of them, it will be impossible to 

 distinguish them wholly from the first, for all popular 

 beliefs (from which many technical and professional 

 beliefs do not differ essentially) derive much of their 

 weight from their general prevalence. We can only 

 ask what fallacies predisposed men to these beliefs, 

 and thus enabled the beliefs to become prevalent. 



The most prolific of these fallacies are false theories. 

 In discussing scientific theories in Chapter V, we saw 

 that in their ultimate nature they are not very different 

 from any other and unscientific attempt to explain things. 

 A theory which suggests that A and B might be connected 

 predisposes to the belief that A and B are connected. An 

 extreme example of unscientific theories is provided by 

 the superstitions and magical beliefs of primitive civiliza- 

 tion. They have ceased to be held explicitly, but they 

 still exert an influence, which is not generally appreciated, 

 on popular beliefs. Thus many people believe, and are 

 very indignant when the assertion is denied, that the 

 poker laid across the bars of the grate will draw up 

 the fire. The belief is based on the old doctrine of the 

 magical power of the cross, formed in this instance by 

 the poker and the bars ; old people can still be found 



