204 THE PRINCIPLES OF SCIENCE 



As the state of doubt is intensely disagreeable, communities try to 

 get rid of it in diverse ways, through ridicule, forcible sunpression, 

 and the like. The method of science seeks to conquer doubt by cul- 

 tivating it and encouraging it to grow until it finds its natural limits 

 and can go no further. Sober reflection soon shows that though very 

 few propositions are in themselves absolutely unquestionable, the pos- 

 sibility of systematic truth cannot be impugned. 



The last sentence of Cohen's statement is of pivotal importance. A 

 rampant Pyrrhonism was no small factor in the decline of ancient 

 science. Unalloyed doubt, eventuating in nothing but a paralyzing 

 awareness of the possibility of error, is as fatal as the complete as- 

 surance remarked by Nietzsche. Implicit in all action is necessarily 

 the possibility of wrong action: we can be certain we have done 

 nothing wrong only by taking care to do nothing at all. Science can 

 progress in its pursuit of truth only as it passes over from timid 

 avoidance to bold acceptance of the risk— nay, the certainty— of error. 



LEARNING PRESUPPOSES ERROR 



We find in Genesis that learning presupposes failure, error; and 

 Carr's maze-running tests show that, for men as for mice, learning 

 occurs only when the subjects are allowed to make and recognize 

 their errors. Learning thus presupposes error and, as itself a process 

 of learning, science presupposes error. Not simply accommodating 

 ourselves to the possibility of error, we actively court error ( e.g., by 

 the extreme generalization of our laws and theories). Only through 

 error, recognized as such, can we hope to learn. "The capacity of 

 learning from experience," says William James, "is one of the rarest 

 gifts of genius." The learning act that both demands and manifests 

 such genius may be precisely that first difficult detection of error in 

 an erstwhile indubitable. The policy of science is to maximize the 

 possibility of learning by minimizing the number of "truths" held 

 permanently beyond any challenge posed by experience. In ener- 

 getic pursuit of the infallibility we confidently suppose humanly 

 approachable, we can advance only to the extent that we deny our- 

 selves the illusion that any item of infallibility is already attained. 



Popper holds it a point of fundamental importance— to the philos- 

 ophy of science no less than to the methodology of science— that the 

 distinguishing characteristic of an empirical statement is its suscepti- 

 bility to falsification. Stipulating that all scientific beliefs must be 



