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organisms in a stage of evolution so primitive that 

 we may suppose immediate pleasantness of sensation 

 to have been their sole incentive to action. To such 

 organisms it might be of no importance whether a 

 stimulus were, or were not, external ; but beyond 

 this stage it seems evident that no animal could 

 maintain itself in life if it did not act upon the vast 

 majority of its sensations as though they were due 

 to external stimuli. Those organisms whose nervous 

 systems reacted in this way most readily, would have 

 a decisive advantage, and this is fully sufficient to 

 account for their transmitting, to their descendants, 

 nervous systems which react, normally, in the same 

 manner. It will, I think, be found that when action 

 is to be taken, a mental reference to an external 

 world can hardly be avoided ; though in the case 

 of dreams, hallucinations and like, where no action 

 is involved, we may be able to dispense with the 

 idea of the externality of the stimulus. 



Recurring once more to the main subject ; the 

 simple and direct syntax has been shown to con- 

 stitute the basis of all that has been accepted as 

 true in science, and reasons . have been given for 

 supposing that it represents the line of development 

 of nervous function which was most conducive to 

 survival, at least among animals ; but I do not 

 suggest that it is the only form of syntax prevalent 

 among men, or even that, for other than scientific 

 purposes, it is at all universally regarded as the 



