EVOLUTION THE MASTER-KEY 



bly presupposes a good digestion. Though entire 

 ly non-rational, it is capable of a rational expla 

 nation. It is now known that the most impor 

 tant of the various &quot;senses&quot; which supplement 

 the familiar five is dependent upon the innumer 

 able sensory nerves which proceed from the in 

 ternal organs to the brain. In health, these nerves 

 combine to produce the &quot; organic sense of well- 

 being,&quot; the perversion and reversal of which are 

 the characteristic feature common to all forms 

 of melancholia. In other states, such as certain 

 forms of mania, and in ecstasy, this sense may be 

 heightened, but not reversed. In health, then, 

 every man has an organic bias towards optimism. 

 The overwhelming majority of people, whose nor 

 mal health is not qualified even by the &quot;malady 

 of thought,&quot; are therefore optimists in virtue of 

 their &quot;organic sense of well-being.&quot; This variety 

 of optimism is, as I have said, entirely non-rational, 

 and thus may be compatible with a belief in hell, 

 which no sympathetic person could realize without 

 loss of his sanity, not to mention his optimism. 

 But so powerful is the control exercised by the 

 organic sensations over the higher faculties of 

 most of us, that, given healthy viscera, it may be 

 doubted whether the imagination is capable of 

 realizing and explicitly appreciating the unspeak 

 able ghastliness of such a belief. In describing 

 gastric optimism as non-rational, however, I do 

 not mean to stigmatize it. Granted that not one 

 per cent, of the population thinks about the things 



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