HYPOTHESIS 149 



scientist : &quot; On entering the laboratory leave your imagination 

 with your overcoat in the vestibule, but take it with you again 

 on your departure&quot;. 1 That is to say: reflect on your experi 

 ments and observations, and conceive and test hypotheses about 

 them ; but never allow your hypotheses to influence your actual 

 reading of the facts when you are observing or experimenting. 



2. // ought to be self -consistent, and free from conflict either with 

 established truths or undoubted facts. Truth cannot oppose truth. 

 Hence the demand for consistency, freedom from internal con 

 tradiction, intelligibility. This, as we have seen, is not to be 

 confounded with imaginability (228). 



Again, the hypothesis must not contradict other established 

 truths or laws. Caution is needed, however, to make sure that 

 the contradiction is real, that it cannot be eliminated by any 

 possible restatement of such laws: for, sometimes an hypothesis 

 sheds a new light on an established law and leads to a more ac 

 curate or more extended formulation of the latter. Sometimes, 

 too, what is commonly believed to be an &quot; established law &quot; is in 

 reality a false and misleading theory,^, the Ptolemaic Astronomy. 



In comparing our hypothesis with facts, the chief danger to 

 be avoided is a prejudiced interpretation or reading of the facts, 

 in favour of the hypothesis. If we find that facts are not in 

 accordance with our hypothesis, we must not say &quot; so much the 

 worse for the facts,&quot; but rather &quot; so much the worse for the 

 hypothesis &quot;. On the other hand, however, we need not reject 

 our hypothesis until we are sure that it is really incompatible 

 with the facts. And here we must take care that what we have 

 regarded as facts are not already mixed with half-unconscious 

 theories or interpretations which, in the light of our present hypo 

 thesis, we may now be able to eliminate from the mixture, and 

 so leave the residue of real fact compatible with our present hypo 

 thesis. 2 Much, if not all, of what we commonly call &quot; fact,&quot; is in 

 timately interwoven with what are really interpretations or theories ; 

 and some of these may have been false from the start. Mere 

 fact cannot be, interpreted fact must be, either true or false. 

 Hence we apply the name &quot;fact&quot; to what we believe to be a 

 truth, a true interpretation of fact (248). And in some of these 

 we may be mistaken, as people were when they regarded it as a 

 &quot; fact &quot; that the sun goes round the earth. When, therefore, we 



1 CLAUDE BKRNARD, Introduction a Vetudc de la midecine experimental, p. 44. 

 3 C/. JOSEPH, of&amp;gt;. cit., pp. 432-3. 



