152 GENERAL YIEW AND BASIS OF SCIENTIFIC RESEARCH. 



disregard them on that account. New truths are often 

 but slowly perceived, and many great discoveries have 

 arisen from what appeared at the outset to be but slightly 

 probable hypotheses ; Avogadro's law, for example. 1 

 Many false beliefs also have at first been doubted, as 

 being only probably false, but finally proved to be so ; 

 the theory of phlogiston, for instance. Any statement 

 which does not actually contradict the fundamental laws 

 of nature is not impossible, even though we are unable to 

 prove it ; and a belief is not necessarily a false or dubious 

 one because we have not sufficient data upon which to 

 base it, or no good argument to support it. With nothing 

 to prove and nothing to disprove a scientific statement, 

 the probability of its truth or falsity are equal. A weak 

 argument in support of a scientific conclusion does not 

 disprove the conclusion ; and a strong argument, based 

 upon many uncertain data, is itself extremely uncertain. 

 To an unscientific mind, statements which are not provable 

 often produce a stronger conviction of probability and 

 truth than those which can be verified ; and this, in some 

 cases, arises partly from the fact that in scientific matters, 

 external appearances are often the opposite of reality. 



In drawing conclusions as to the degree of probability 

 of a given scientific statement, it is necessary to value, as 

 far as possible, each point of evidence according to its own 

 intrinsic degree of likelihood ; and in forming a general 

 scheme of .science, we also require to quantify our ideas, 

 and to value different scientific principles according to 

 their relative probable degrees of intrinsic importance. 



1 See p. 180. 



