THE LOGIC OF SCIENCE 401 



criticism. On the contrary it seems to grow all the faster for 

 cutting itself loose from what has always been believed, plung- 

 ing into an agitated sea of wild hypotheses and hazardous experi- 

 ments, and hailing as "true" whatever belief most successfully 

 emerges from the rough and tumble of the conflict of opinions. 



What then is the solution of the paradox that the prosperity 

 of science seems to depend on its ignoring all the rules laid 

 down for its guidance in the traditional logic? Simply this, 

 that the traditional logic is wrong in all its regulations, that 

 scientific practice is right, and that logical theory should be based 

 on scientific practice. The pragmatist is the philosopher who 

 has grasped all this and has therefore discarded the meaning- 

 less ideals of an impracticable " logic." He has recognised 

 instead that certainty is not the " presupposition " of scientific 

 inquiry but its (distant) aim, and that no matter how much 

 confirmation a scientific theory acquires, it can never become 

 absolutely certain. He willingly admits the "formal fallacy" 

 involved in " verification," but does not draw the formal 

 logician's inference therefrom. Instead of inferring that there- 

 fore empirical evidence can never be conclusive, that experi- 

 ence can never " prove " anything, he infers that since science 

 nevertheless accumulates such stores of valuable truth, it must 

 be possible to dispense with evidence coming up to the logician's 

 specifications and with the logical ideal of " proof." An ever- 

 growing probability, sufficient for the purposes of the science, 

 must be what " certainty " really means in the concrete, and the 

 existence of alternative explanations and rival probabilities 

 must be recognised in theory, as in fact. 



Logic, in other words, must assimilate the great dictum of 

 Sir J. J. Thomson that " a scientific theory is a policy and not a 

 creed," and modify itself accordingly. If truth (like honesty) is 

 the best policy, our keenness to attain it will be enhanced ; but 

 so will the (apparent) difficulties of ensuring that we are pursuing 

 the best policy and picking it out from among the alterna- 

 tives that present themselves. For we clearly run the risk that 

 by adopting one policy we blind ourselves to the good that is in 

 the others and to the facts that they could bring to light. T6 

 minimise this risk, it is evident that science must systematically 

 cultivate open-mindedness and practise toleration. Alternative 

 theories must always be borne in mind, even when the known 

 facts are on the whole against them, and no working theory 



