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TEE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



able to comprehend it after all the explanations 

 which it is possible to give. As ray whole dis- 

 course will be misleading unless all my hearers 

 have a clear conception of it, I shall endeavor to 

 present you with the materials of such a concep- 

 tion, rather in the form of concrete illustrations 

 in familiar language than in that of abstract 

 general definitions. 



As one mode of expression, we might say 

 that modern science introduces into the higher 

 modes of thought about Nature that same kind 

 of practical good sense which characterizes the 

 successful man of business. Scientific inves- 

 tigation is, in a certain sense, purely practical 

 in both its methods and its aims. There is a 

 mental operation, with which all are well ac- 

 quainted, under the familiar term " theorizing." 

 To this operation all scientific investigation is so 

 much opposed that the mere theorizer and essay- 

 ist can never make any real advance in the knowl- 

 edge of Nature. To speak with a little more 

 precision, we may say that, as science only deals 

 with phenomena and the laws which connect 

 them, so all the terms which it uses have exact 

 literal meanings, and refer only to things which 

 admit of being perceived by the senses, or, at 

 least, of being conceived as thus perceptible. This 

 use of plain language appears to be an actual 

 source of difficulty with some in trying to under- 

 stand the philosophy of science. Long habit in 

 the use of figurative language in which ideas not 

 readily comprehensible are symbolized by com- 

 mon terms leads one to look for hidden mean- 

 ings in all philosophic discourse, and to see dif- 

 ficulties in terms which, to a scientific thinker, 

 are as plain and matter of fact as an order for 

 breakfast to an hotel- waiter. 



We might also say that no question is a sci- 

 entific one which does not in some way admit 

 of being tested by experience. The single ob- 

 ject of scientific research is to predict the 

 course of Nature, or the results of those artifi- 

 cial combinations of causes which we call ex- 

 periments ; and no question is a scientific one 

 unless its solution will in some way advance 

 this object. I must not, however, be under- 

 stood 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 10,000 years ago is a scientific one, 

 because it is one respecting actual historic occur- 

 rence 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 further, and inquire 

 whether these 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 

 be made evident to the senses of others. From 

 the very nature of things, it could leave no ma- 

 terial trace of itself, to be unearthed by the 

 geologist 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 ; much less can science consider those of 

 past generations. 



There is, thus, a quite well-defined limit be- 

 tween questions which are scientific ones and 

 those which are not scientific, and with which, 

 in consequence, science has no concern what- 

 ever. 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 respect- 

 ing sensible things, without in any manner ad- 

 vancing their solutions. 



This limitation of all scientific research to a 

 single specific field is something so little under- 

 stood that I may have occasion to call it to mind 

 in other connections. But there is another equal- 

 ly essential maxim of science which I must ex- 

 plain, in order that you may understand the 

 spirit which animates scientific investigation. It 

 is that the man of science as such has no pre- 

 conceived theories to support, but simply goes to 

 Nature, to find out and interpret what she has to 

 say according to her exact meaning. What he 

 may wish to be true has no bearing at all on the 

 question of what really is true. Here arises the 

 inability of men of science to view theological 

 questions in a light which shall be satisfactory to 

 the theologians, and the corresponding inability 

 of the latter to appreciate the spirit in which 

 men of science discuss the problems of life and 

 being. We hear much at the present time of a 

 supposed conflict between science and religion ; 

 but it is rather a conflict between two sets of 

 men, who view Nature from opposite and irrec- 

 oncilable standpoints. It is essential to the un- 

 derstanding of our theme that we should see in 



