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SCIENCE 



[N. S. Vol. XXXIII. No. 



much time killing off and burying older 

 erroneous interpretations. The business is 

 seldom accomplished by direct attack, for 

 error perishes only in the light of truth, as 

 microorganisms are said to perish suddenly 

 when struck by ultra-violet rays. Owing 

 to the load of false theories, we Avork like a 

 mental chain-gang and are never unfet- 

 tered. The handicap imposed by wrong 

 hypotheses has always impeded the growth 

 of science. Allusion to a few celebrated 

 instances will suiSce. Phlogiston long pre- 

 vented chemistry from becoming the peer 

 of other sciences. It was a notion which 

 remained alive and dominant until Lavoi- 

 sier rendered it a mere historical curiosity, 

 by discovering the true principle of com- 

 bustion. The corpuscular theory of light, 

 upheld by Newton, long retarded physics. 

 It was got rid of, not by proving it false, 

 but by proving the undulatory theory true. 

 The doctrine of the special creation and 

 fixity of species was universally accepted, 

 although utterly without justification. It 

 vanished from science when the true doe- 

 trine of evolution was convincingly estab- 

 lished. The hypothesis that great epidem- 

 ics are due to diseases spread by smell, 

 although only the bad guess of ignorance, 

 lasted until modern bacteriology showed 

 us the real causes of infection. 



The multitude of such experiences, great 

 and small, has gradually created among 

 scientific men a special highly character- 

 istic mental attitude. They regard the 

 majority of the accumulated data and 

 many of the inductions of science as cor- 

 rect. This is their estimate of the great 

 body of information which, though per- 

 sonal in its origin, has been in the course 

 of time, so tested and verified that it is 

 looked upon as established and secure. 

 When Asellus in 1622 discovered the 

 lymphatics or so-called laeteals of the mes- 

 entery and demonstrated that they convey 



products of digestion from the intestine, 

 his knowledge was his own, and at first his 

 only. Since then the observations have 

 been so repeatedly verified and of course 

 extended that all uncertainty has vanished 

 from our minds. Similarly in innumer- 

 able other cases reasonable impersonal cer- 

 tainty has been attained. Yet the investi- 

 gator lives in an atmosphere of concen- 

 trated uncertainty, for he is convinced 

 that at any time new data may turn up, 

 and that all generalizations are likely to 

 require modification. "We might well 

 adopt as our cry — Incredulity towards the 

 known; open credulity towards the un- 

 known. 



We think of science as a vast series of 

 approximations and our task is constantly 

 to render our approximations closer to 

 absolute truth, the existence of which we 

 take for granted. We use our approxima- 

 tions as best we may, treating them in 

 large part and at least for the time being 

 as if they were accurately true, yet mean- 

 while we remain alert to better them. This 

 has long been the standard of scientific 

 thought. It is the pragmatic attitude of 

 mind, but its new name has not rendered 

 it a novelty. 



The pivot of all research is adequate 

 proof. It would certainly aid science if 

 some competent philosopher should make a 

 study of the practise of investigators in the 

 various branches of science sufficient to 

 render clear the general principles, by 

 which investigators decide when a new ob- 

 servation or a new induction is sufficiently 

 proven. If we follow the advance of re- 

 search in any particular direction we soon 

 realize that there is a more or less definite 

 standard of proof, which, though never 

 clearly formulated, is none the less insisted 

 upon, so that any paper which does not 

 come up to this standard is subject to un- 

 favorable criticism. Two elements of this 



