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unless its solution will in some way advance this object. I must 

 not, however, be understood as saying that the test of experience 

 can always be immediately applied, because then no disputed 

 question could be a scientific one. For example, the question 

 whether man existed on the earth 50,000 years ago is a scientific 

 one, because it is one respecting actual historic occurrence of 

 scenes evident to the senses. It could at once be settled by 

 simple inspection, could we in any way form a picture of the earth 

 as it then looked, and it may actually be settled in the future by 

 the presence or absence of sensible traces of the existence of man 

 at those times. Should we, however, go farther, and inquire 

 whether such men had souls, our inquiry would not be a scientific 

 one, nor one in which science could in any way concern itself with 

 profit. The soul can neither be seen, nor in any way made evi- 

 dent to the senses of others. From the very nature of things, it 

 could leave no material trace of- itself to be unearthed by the geol- 

 ogist or antiquarian of a future age. So far are we from forming 

 any conception even of our own souls, as sensible existences, that 

 no question affecting them, even now, is a scientific one ; milch 

 less can science consider those of past generations. 



There is thus a quite well defined limit between questions which 

 are scientific ones and those which are not scientific, and with 

 which, in consequence, science has no concern whatever. You 

 must not understand me as in any way claiming that questions of 

 this last class are not worth thinking about. They include many 

 which are of the most absorbing interest to the human race, and 

 about which men will think the more as they become more thought- 

 ful. But to mix them with scientific discussions will only introduce 

 confusion of thought respecting sensible things, without in any 

 manner advancing their solutions. The current desires that^ sci- 

 ence shall consider man as something more than an animal are as 

 unreasonable as if we wanted to make algebra a help to moral 

 philosophy. 



This limitation of all scientific research to a single specific field 

 is something so little understood, that I may have occasion to call 

 it to mind in other connections. But, there is another equally 

 essential maxim of science which I must explain in order that you 

 may understand the spirit which animates scientific investigation. 

 It is, that the man of science, as such, has no preconceived theories 

 to support, but simply goes' to nature to find out and interpret 



