MAN AS THE INTERPRETER OF NATURE. 6S9 



inon-sense," as to matters on which there seems no room for difference 

 of opinion, because every sane person comes to the same conclusion, 

 although he may he able to give no other reason for it than that it 

 appears to him " self-evident." Thus, while philosophers have raised 

 a thick cloud of dust in the discussion of the basis of our belief in the 

 existence of a world external to ourselves of the Non-Esio, as distinct 

 from the Ego and while every logician claims to have found some 

 flaw in the proof advanced by every other, the common-sense of man- 

 kind has arrived at a decision that is practically worth all the argu- 

 ments of all the philosophers who have fought again and again over 

 this battle-ground. And I think it can be shown that the trustworthi- 

 ness of this common-sense decision arises from its dependence, not on 

 any one set of experiences, but upon our unconscious coordination of 

 the whole aof2:reo;ate of our experiences not on the conclusiveness of 

 any one train of reasoning, but on the convergence of all our lines of 

 thought toward this one centre. 



Now, this " common-sense," disciplined and enlarged by appropri- 

 ate culture, becomes one of our most valuable instruments of scientific 

 inquiry ; affording in many instances the best, and sometimes the only, 

 basis for a rational conclusion. Let us take as a typical case, in which 

 no special knowledge is required, what we are accustomed to call the 

 " flint implements " of the Abbeville and Amiens gravel-beds. No 

 logical proof can be adduced that the peculiar shapes of these flints 

 were given to them by human hands; but does any unprejudiced per- 

 son now doubt it? The evidence of design, to which, after an exami- 

 nation of one or two such specimens, we should only be justified in 

 attaching a probable value, derives an irresistible cogency from accu- 

 mulation. On the other hand, the improbability that these flints ac- 

 quired their peculiar shape by accident becomes to our minds greater 

 and greater as more and more such specimens are found ; until at last 

 this hypothesis, although it cannot be directly disproved, is felt to be 

 almost inconceivable, except by minds previously " possessed " by the 

 " dominant idea " of the modern origin of man. And thus what was 

 in the first instance a matter of discussion has now become one of 

 those " self-evident " propositions which claim the unhesitating assent 

 of all whose opinion on the subject is entitled to the least weight. 



We proceed upward, however, from such questions as the common- 

 sense of mankind generally is competent to decide, to those in which 

 special knowledge is required to give value to the judgment ; and thus 

 the interpretation of Nature by the use of that facvdty comes to be 

 more and more individual ; things being perfectly " self-evident " to 

 men of special culture which ordinary men, or men whose training has 

 lain in a different direction, do not apprehend as such. Of all depart- 

 ments of science, geology seems to me to be the one that most depends 

 on this specially-trained " common-sense ; " which brings as it were 

 into one focus the light afforded by a great variety of studies physi- 

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