182 WHAT IS SCIENCE? 



which there is no doubt, is inconsistent with some 

 " theory," then the " theory " (whether it is a law or 

 what we call a theory) is false and there is an end of it. 

 But it may easily happen, and does often happen, that 

 a " theory " is misinterpreted by those who fail to 

 understand it ; it appears to predict something incon- 

 sistent with practice only because its real meaning is 

 not grasped. It is certainly true that those who do not 

 understand " theory " had better leave it alone ; reliance 

 on misunderstood theory is certainly quite as dangerous 

 as reliance on uninstructed " practice." 



And here we come to the conclusion about the relation 

 of science to everyday life, which it seems to me most 

 important to enforce. Those unversed in the ways of 

 science often regard it as a body of fixed knowledge con- 

 tained in text -books and treatises, from which anyone 

 who takes the trouble can extract all the information on 

 any subject which science has to offer ; they think of it 

 as something that can be learnt as the multiplication 

 table can be learnt, and consider that anyone who has 

 " done " science at school or college is complete master 

 of its mysteries. Nothing could be further from the 

 truth regarding science applied to practical problems. 

 It is scarcely ever possible, even for the most learned 

 student, to offer a complete and satisfying explanation 

 of any difficulty, merely on the basis of established know- 

 ledge ; there is also some element in the problem which 

 has not yet engaged scientific attention. Applied science, 

 like pure science, is not a set of immutable principles 

 and propositions ; it is rather an instrument of thought 

 and a way of thinking. Every practical problem is really 

 aT problem irTresearch, leading to the advancement of 

 pure learning as well as to material efficiency ; indeed 

 almost all the problems by the solution of which science 

 has actually advanced have been suggested, more or less 

 directly, by the familiar experiences of everyday life 



