SELECTION OF BELIEFS. 99 



because we can only direct the power of attention to that 

 which is true and important by means of a previous 

 knowledge of what is true and important, and what par- 

 ticular evidence ought to be attended to, i.e. by cultiva- 

 tion of the intellectual power of selecting ideas, and of 

 determining their relative degrees of importance in any 

 given case. 



True scientific belief is based upon reason, i.e. upon 

 suitable and sufficient evidence. Upon such a basis it 

 may be affirmed 



1. That it is a moral duty to believe any scientific 



statement which is logically absolute, matUe- 

 matically demonstrable, or experimentally or 

 observationally verifiable provided, of course, 

 that we have had an opportunity of perceiving 

 and understanding the evidence. 



2. As life is too short to enable us to verify extensively 



more than a very small fraction of our scientific 

 beliefs, we may reasonably and justifiably believe 

 what we do not know, provided the statement 

 which we perceive is not only not contradicted 

 by any of the fundamental laws of the sciences 

 but is in perfect accordance with and supported 

 by them. We may also believe scientific state- 

 ments made by good authorities. 



3. We are equally bound to hold our belief in suspense 



respecting any scientific statement or hypothesis 

 for the support of which there exists no definite 

 evidence, or in relation to which the evidence for 

 and against appears equally strong, even although 

 it does not' contradict any of those laws. We are 

 not morally bound to believe a doctrine in support 



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